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/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE libopusfile SOFTWARE CODEC SOURCE CODE. *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE libopusfile SOURCE CODE IS (C) COPYRIGHT 2012                *
 * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
 *                                                                  *
 ********************************************************************/
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#include "internal.h"
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <string.h>

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/*RFCs referenced in this file:
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  RFC  761: DOD Standard Transmission Control Protocol
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  RFC 1535: A Security Problem and Proposed Correction With Widely Deployed DNS
   Software
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  RFC 1738: Uniform Resource Locators (URL)
  RFC 1945: Hypertext Transfer Protocol -- HTTP/1.0
  RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1
  RFC 2145: Use and Interpretation of HTTP Version Numbers
  RFC 2246: The TLS Protocol Version 1.0
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  RFC 2459: Internet X.509 Public Key Infrastructure Certificate and
   Certificate Revocation List (CRL) Profile
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  RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1
  RFC 2617: HTTP Authentication: Basic and Digest Access Authentication
  RFC 2817: Upgrading to TLS Within HTTP/1.1
  RFC 2818: HTTP Over TLS
  RFC 3492: Punycode: A Bootstring encoding of Unicode for Internationalized
   Domain Names in Applications (IDNA)
  RFC 3986: Uniform Resource Identifier (URI): Generic Syntax
  RFC 3987: Internationalized Resource Identifiers (IRIs)
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  RFC 4343: Domain Name System (DNS) Case Insensitivity Clarification
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  RFC 5894: Internationalized Domain Names for Applications (IDNA):
   Background, Explanation, and Rationale
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  RFC 6066: Transport Layer Security (TLS) Extensions: Extension Definitions
  RFC 6125: Representation and Verification of Domain-Based Application Service
   Identity within Internet Public Key Infrastructure Using X.509 (PKIX)
   Certificates in the Context of Transport Layer Security (TLS)*/
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typedef struct OpusParsedURL   OpusParsedURL;
typedef struct OpusStringBuf   OpusStringBuf;
typedef struct OpusHTTPConn    OpusHTTPConn;
typedef struct OpusHTTPStream  OpusHTTPStream;

static char *op_string_range_dup(const char *_start,const char *_end){
  size_t  len;
  char   *ret;
  OP_ASSERT(_start<=_end);
  len=_end-_start;
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  /*This is to help avoid overflow elsewhere, later.*/
  if(OP_UNLIKELY(len>=INT_MAX))return NULL;
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  ret=(char *)_ogg_malloc(sizeof(*ret)*(len+1));
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  if(OP_LIKELY(ret!=NULL)){
    memcpy(ret,_start,sizeof(*ret)*(len));
    ret[len]='\0';
  }
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  return ret;
}

static char *op_string_dup(const char *_s){
  return op_string_range_dup(_s,_s+strlen(_s));
}

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static char *op_string_tolower(char *_s){
  int i;
  for(i=0;_s[i]!='\0';i++){
    int c;
    c=_s[i];
    if(c>='A'&&c<='Z')c+='a'-'A';
    _s[i]=(char)c;
  }
  return _s;
}

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/*URI character classes (from RFC 3986).*/
#define OP_URL_ALPHA \
 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
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#define OP_URL_DIGIT       "0123456789"
#define OP_URL_HEXDIGIT    "0123456789ABCDEFabcdef"
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/*Not a character class, but the characters allowed in <scheme>.*/
#define OP_URL_SCHEME      OP_URL_ALPHA OP_URL_DIGIT "+-."
#define OP_URL_GEN_DELIMS  "#/:?@[]"
#define OP_URL_SUB_DELIMS  "!$&'()*+,;="
#define OP_URL_RESERVED    OP_URL_GEN_DELIMS OP_URL_SUB_DELIMS
#define OP_URL_UNRESERVED  OP_URL_ALPHA OP_URL_DIGIT "-._~"
/*Not a character class, but the characters allowed in <pct-encoded>.*/
#define OP_URL_PCT_ENCODED "%"
/*Not a character class or production rule, but for convenience.*/
#define OP_URL_PCHAR_BASE \
 OP_URL_UNRESERVED OP_URL_PCT_ENCODED OP_URL_SUB_DELIMS
#define OP_URL_PCHAR       OP_URL_PCHAR_BASE ":@"
/*Not a character class, but the characters allowed in <userinfo> and
   <IP-literal>.*/
#define OP_URL_PCHAR_NA    OP_URL_PCHAR_BASE ":"
/*Not a character class, but the characters allowed in <segment-nz-nc>.*/
#define OP_URL_PCHAR_NC    OP_URL_PCHAR_BASE "@"
/*Not a character clsss, but the characters allowed in <path>.*/
#define OP_URL_PATH        OP_URL_PCHAR "/"
/*Not a character class, but the characters allowed in <query> / <fragment>.*/
#define OP_URL_QUERY_FRAG  OP_URL_PCHAR "/?"

/*Check the <% HEXDIG HEXDIG> escapes of a URL for validity.
  Return: 0 if valid, or a negative value on failure.*/
static int op_validate_url_escapes(const char *_s){
  int i;
  for(i=0;_s[i];i++){
    if(_s[i]=='%'){
      if(OP_UNLIKELY(!isxdigit(_s[i+1]))
       ||OP_UNLIKELY(!isxdigit(_s[i+2]))
       /*RFC 3986 says %00 "should be rejected if the application is not
          expecting to receive raw data within a component."*/
       ||OP_UNLIKELY(_s[i+1]=='0'&&_s[i+2]=='0')){
        return OP_FALSE;
      }
      i+=2;
    }
  }
  return 0;
}

/*Convert a hex digit to its actual value.
  _c: The hex digit to convert.
      Presumed to be valid ('0'...'9', 'A'...'F', or 'a'...'f').
  Return: The value of the digit, in the range [0,15].*/
static int op_hex_value(int _c){
  return _c>='a'?_c-'a'+10:_c>='A'?_c-'A'+10:_c-'0';
}

/*Unescape all the <% HEXDIG HEXDIG> sequences in a string in-place.
  This does no validity checking.*/
static char *op_unescape_url_component(char *_s){
  int i;
  int j;
  for(i=j=0;_s[i];i++,j++){
    if(_s[i]=='%'){
      _s[i]=(char)(op_hex_value(_s[i+1])<<4|op_hex_value(_s[i+2]));
      i+=2;
    }
  }
  return _s;
}

/*Parse a file: URL.
  This code is not meant to be fast: strspn() with large sets is likely to be
   slow, but it is very convenient.
  It is meant to be RFC 1738-compliant (as updated by RFC 3986).*/
static const char *op_parse_file_url(const char *_src){
  const char *scheme_end;
  const char *path;
  const char *path_end;
  scheme_end=_src+strspn(_src,OP_URL_SCHEME);
  if(OP_UNLIKELY(*scheme_end!=':')
   ||scheme_end-_src!=4||op_strncasecmp(_src,"file",4)!=0){
    /*Unsupported protocol.*/
    return NULL;
  }
  /*Make sure all escape sequences are valid to simplify unescaping later.*/
  if(OP_UNLIKELY(op_validate_url_escapes(scheme_end+1)<0))return NULL;
  if(scheme_end[1]=='/'&&scheme_end[2]=='/'){
    const char *host;
    /*file: URLs can have a host!
      Yeah, I was surprised, too, but that's what RFC 1738 says.
      It also says, "The file URL scheme is unusual in that it does not specify
       an Internet protocol or access method for such files; as such, its
       utility in network protocols between hosts is limited," which is a mild
       understatement.*/
    host=scheme_end+3;
    /*The empty host is what we expect.*/
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    if(OP_LIKELY(*host=='/'))path=host;
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    else{
      const char *host_end;
      char        host_buf[28];
      /*RFC 1738 says localhost "is interpreted as `the machine from which the
         URL is being interpreted,'" so let's check for it.*/
      host_end=host+strspn(host,OP_URL_PCHAR_BASE);
      /*No <port> allowed.
        This also rejects IP-Literals.*/
      if(*host_end!='/')return NULL;
      /*An escaped "localhost" can take at most 27 characters.*/
      if(OP_UNLIKELY(host_end-host>27))return NULL;
      memcpy(host_buf,host,sizeof(*host_buf)*(host_end-host));
      host_buf[host_end-host]='\0';
      op_unescape_url_component(host_buf);
      op_string_tolower(host_buf);
      /*Some other host: give up.*/
      if(OP_UNLIKELY(strcmp(host_buf,"localhost")!=0))return NULL;
      path=host_end;
    }
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  }
  else path=scheme_end+1;
  path_end=path+strspn(path,OP_URL_PATH);
  /*This will reject a <query> or <fragment> component, too.
    I don't know what to do with queries, but a temporal fragment would at
     least make sense.
    RFC 1738 pretty clearly defines a <searchpart> that's equivalent to the
     RFC 3986 <query> component for other schemes, but not the file: scheme,
     so I'm going to just reject it.*/
  if(*path_end!='\0')return NULL;
  return path;
}

#if defined(OP_ENABLE_HTTP)
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#ifndef _WIN32
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# include <sys/ioctl.h>
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# include <sys/types.h>
# include <sys/socket.h>
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# include <sys/timeb.h>
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# include <arpa/inet.h>
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# include <netinet/in.h>
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# include <netinet/tcp.h>
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# include <fcntl.h>
# include <netdb.h>
# include <poll.h>
# include <unistd.h>
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#define ERRNO() errno
#define CLOSE(fd) close(fd)
#define IOCTL(fd,req,...) ioctl(fd,req,__VA_ARGS__)
#define GETSOCKOPT(fd,lvl,name,val,len) getsockopt(fd,lvl,name,val,len)
#define SETSOCKOPT(fd,lvl,name,val,len) getsockopt(fd,lvl,name,val,len)
#define FTIME(x) ftime(x)
#else /* _WIN32 */
#include <winsock2.h>
#include <ws2tcpip.h>
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#include "winerrno.h"
#include "wsockwrapper.h"
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#define ERRNO() (WSAGetLastError() - WSABASEERR)
#define CLOSE(x) closesocket(x)
#define IOCTL(fd,req,arg) ioctlsocket(fd,req,(u_long*)(arg))
#define GETSOCKOPT(fd,lvl,name,val,len) \
    getsockopt(fd,lvl,name,(char*)(val),len)
#define SETSOCKOPT(fd,lvl,name,val,len) \
    setsockopt(fd,lvl,name,(const char*)(val),len)
#define FTIME(x) win32_ftime(x)
#endif /* _WIN32 */
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# include <openssl/ssl.h>
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# include <openssl/x509v3.h>
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/*The maximum number of simultaneous connections.
  RFC 2616 says this SHOULD NOT be more than 2, but everyone on the modern web
   ignores that (e.g., IE 8 bumped theirs up from 2 to 6, Firefox uses 15).
  If it makes you feel better, we'll only ever actively read from one of these
   at a time.
  The others are kept around mainly to avoid slow-starting a new connection
   when seeking, and time out rapidly.*/
# define OP_NCONNS_MAX (4)

/*The number of redirections at which we give up.
  The value here is the current default in Firefox.
  RFC 2068 mandated a maximum of 5, but RFC 2616 relaxed that to "a client
   SHOULD detect infinite redirection loops."
  Fortunately, 20 is less than infinity.*/
# define OP_REDIRECT_LIMIT (20)

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/*The initial size of the buffer used to read a response message (before the
   body).*/
# define OP_RESPONSE_SIZE_MIN (510)
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/*The maximum size of a response message (before the body).
  Responses larger than this will be discarded.
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  I've seen a real server return 20 kB of data for a 302 Found response.
  Increasing this beyond 32kB will cause problems on platforms with a 16-bit
   int.*/
# define OP_RESPONSE_SIZE_MAX (32766)
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/*The number of milliseconds we will allow a connection to sit idle before we
   refuse to resurrect it.
  Apache as of 2.2 has reduced its default timeout to 5 seconds (from 15), so
   that's what we'll use here.*/
# define OP_CONNECTION_IDLE_TIMEOUT_MS (5*1000)

/*The number of milliseconds we will wait to send or receive data before giving
   up.*/
# define OP_POLL_TIMEOUT_MS (30*1000)

/*We will always attempt to read ahead at least this much in preference to
   opening a new connection.*/
# define OP_READAHEAD_THRESH_MIN (32*(opus_int32)1024)

/*The amount of data to request after a seek.
  This is a trade-off between read throughput after a seek vs. the the ability
   to quickly perform another seek with the same connection.*/
# define OP_PIPELINE_CHUNK_SIZE     (32*(opus_int32)1024)
/*Subsequent chunks are requested with larger and larger sizes until they pass
   this threshold, after which we just ask for the rest of the resource.*/
# define OP_PIPELINE_CHUNK_SIZE_MAX (1024*(opus_int32)1024)
/*This is the maximum number of requests we'll make with a single connection.
  Many servers will simply disconnect after we attempt some number of requests,
   possibly without sending a Connection: close header, meaning we won't
   discover it until we try to read beyond the end of the current chunk.
  We can reconnect when that happens, but this is slow.
  Instead, we impose a limit ourselves (set to the default for Apache
   installations and thus likely the most common value in use).*/
# define OP_PIPELINE_MAX_REQUESTS   (100)
/*This should be the number of requests, starting from a chunk size of
   OP_PIPELINE_CHUNK_SIZE and doubling each time, until we exceed
   OP_PIPELINE_CHUNK_SIZE_MAX and just request the rest of the file.
  We won't reuse a connection when seeking unless it has at least this many
   requests left, to reduce the chances we'll have to open a new connection
   while reading forward afterwards.*/
# define OP_PIPELINE_MIN_REQUESTS   (7)

/*Is this an https URL?
  For now we can simply check the last letter of the scheme.*/
# define OP_URL_IS_SSL(_url) ((_url)->scheme[4]=='s')

/*Does this URL use the default port for its scheme?*/
# define OP_URL_IS_DEFAULT_PORT(_url) \
 (!OP_URL_IS_SSL(_url)&&(_url)->port==80 \
 ||OP_URL_IS_SSL(_url)&&(_url)->port==443)

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struct OpusParsedURL{
  /*Either "http" or "https".*/
  char     *scheme;
  /*The user name from the <userinfo> component, or NULL.*/
  char     *user;
  /*The password from the <userinfo> component, or NULL.*/
  char     *pass;
  /*The <host> component.
    This may not be NULL.*/
  char     *host;
  /*The <path> and <query> components.
    This may not be NULL.*/
  char     *path;
  /*The <port> component.
    This is set to the default port if the URL did not contain one.*/
  unsigned  port;
};

/*Parse a URL.
  This code is not meant to be fast: strspn() with large sets is likely to be
   slow, but it is very convenient.
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  It is meant to be RFC 3986-compliant.
  We currently do not support IRIs (Internationalized Resource Identifiers,
   RFC 3987).
  Callers should translate them to URIs first.*/
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static int op_parse_url_impl(OpusParsedURL *_dst,const char *_src){
  const char  *scheme_end;
  const char  *authority;
  const char  *userinfo_end;
  const char  *user;
  const char  *user_end;
  const char  *pass;
  const char  *hostport;
  const char  *hostport_end;
  const char  *host_end;
  const char  *port;
  opus_int32   port_num;
  const char  *port_end;
  const char  *path;
  const char  *path_end;
  const char  *uri_end;
  scheme_end=_src+strspn(_src,OP_URL_SCHEME);
  if(OP_UNLIKELY(*scheme_end!=':')
   ||OP_UNLIKELY(scheme_end-_src<4)||OP_UNLIKELY(scheme_end-_src>5)
   ||OP_UNLIKELY(op_strncasecmp(_src,"https",scheme_end-_src)!=0)){
    /*Unsupported protocol.*/
    return OP_EIMPL;
  }
  if(OP_UNLIKELY(scheme_end[1]!='/')||OP_UNLIKELY(scheme_end[2]!='/')){
    /*We require an <authority> component.*/
    return OP_EINVAL;
  }
  authority=scheme_end+3;
  /*Make sure all escape sequences are valid to simplify unescaping later.*/
  if(OP_UNLIKELY(op_validate_url_escapes(authority)<0))return OP_EINVAL;
  /*Look for a <userinfo> component.*/
  userinfo_end=authority+strspn(authority,OP_URL_PCHAR_NA);
  if(*userinfo_end=='@'){
    /*Found one.*/
    user=authority;
    /*Look for a password (yes, clear-text passwords are deprecated, I know,
       but what else are people supposed to use? use SSL if you care).*/
    user_end=authority+strspn(authority,OP_URL_PCHAR_BASE);
    if(*user_end==':')pass=user_end+1;
    else pass=NULL;
    hostport=userinfo_end+1;
  }
  else{
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    /*We shouldn't have to initialize user_end, but gcc is too dumb to figure
       out that user!=NULL below means we didn't take this else branch.*/
    user=user_end=NULL;
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    pass=NULL;
    hostport=authority;
  }
  /*Try to figure out where the <host> component ends.*/
  if(hostport[0]=='['){
    hostport++;
    /*We have an <IP-literal>, which can contain colons.*/
    hostport_end=host_end=hostport+strspn(hostport,OP_URL_PCHAR_NA);
    if(OP_UNLIKELY(*hostport_end++!=']'))return OP_EINVAL;
  }
  /*Currently we don't support IDNA (RFC 5894), because I don't want to deal
     with the policy about which domains should not be internationalized to
     avoid confusing similarities.
    Give this API Punycode (RFC 3492) domain names instead.*/
  else hostport_end=host_end=hostport+strspn(hostport,OP_URL_PCHAR_BASE);
  /*TODO: Validate host.*/
  /*Is there a port number?*/
  port_num=-1;
  if(*hostport_end==':'){
    int i;
    port=hostport_end+1;
    port_end=port+strspn(port,OP_URL_DIGIT);
    path=port_end;
    /*Not part of RFC 3986, but require port numbers in the range 0...65535.*/
    if(OP_LIKELY(port_end-port>0)){
      while(*port=='0')port++;
      if(OP_UNLIKELY(port_end-port>5))return OP_EINVAL;
      port_num=0;
      for(i=0;i<port_end-port;i++)port_num=port_num*10+port[i]-'0';
      if(OP_UNLIKELY(port_num>65535))return OP_EINVAL;
    }
  }
  else path=hostport_end;
  path_end=path+strspn(path,OP_URL_PATH);
  /*If the path is not empty, it must begin with a '/'.*/
  if(OP_LIKELY(path_end>path)&&OP_UNLIKELY(path[0]!='/'))return OP_EINVAL;
  /*Consume the <query> component, if any (right now we don't split this out
     from the <path> component).*/
  if(*path_end=='?')path_end=path_end+strspn(path_end,OP_URL_QUERY_FRAG);
  /*Discard the <fragment> component, if any.
    This doesn't get sent to the server.
    Some day we should add support for Media Fragment URIs
     <http://www.w3.org/TR/media-frags/>.*/
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  if(*path_end=='#')uri_end=path_end+1+strspn(path_end+1,OP_URL_QUERY_FRAG);
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  else uri_end=path_end;
  /*If there's anything left, this was not a valid URL.*/
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  if(OP_UNLIKELY(*uri_end!='\0'))return OP_EINVAL;
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  _dst->scheme=op_string_range_dup(_src,scheme_end);
  if(OP_UNLIKELY(_dst->scheme==NULL))return OP_EFAULT;
  op_string_tolower(_dst->scheme);
  if(user!=NULL){
    _dst->user=op_string_range_dup(user,user_end);
    if(OP_UNLIKELY(_dst->user==NULL))return OP_EFAULT;
    op_unescape_url_component(_dst->user);
    /*Unescaping might have created a ':' in the username.
      That's not allowed by RFC 2617's Basic Authentication Scheme.*/
    if(OP_UNLIKELY(strchr(_dst->user,':')!=NULL))return OP_EINVAL;
  }
  else _dst->user=NULL;
  if(pass!=NULL){
    _dst->pass=op_string_range_dup(pass,userinfo_end);
    if(OP_UNLIKELY(_dst->pass==NULL))return OP_EFAULT;
    op_unescape_url_component(_dst->pass);
  }
  else _dst->pass=NULL;
  _dst->host=op_string_range_dup(hostport,host_end);
  if(OP_UNLIKELY(_dst->host==NULL))return OP_EFAULT;
  if(port_num<0){
    if(_src[4]=='s')port_num=443;
    else port_num=80;
  }
  _dst->port=(unsigned)port_num;
  /*RFC 2616 says an empty <abs-path> component is equivalent to "/", and we
     MUST use the latter in the Request-URI.
    Reserve space for the slash here.*/
  if(path==path_end||path[0]=='?')path--;
  _dst->path=op_string_range_dup(path,path_end);
  if(OP_UNLIKELY(_dst->path==NULL))return OP_EFAULT;
  /*And force-set it here.*/
  _dst->path[0]='/';
  return 0;
}

static void op_parsed_url_init(OpusParsedURL *_url){
  memset(_url,0,sizeof(*_url));
}

static void op_parsed_url_clear(OpusParsedURL *_url){
  _ogg_free(_url->scheme);
  _ogg_free(_url->user);
  _ogg_free(_url->pass);
  _ogg_free(_url->host);
  _ogg_free(_url->path);
}

static int op_parse_url(OpusParsedURL *_dst,const char *_src){
  OpusParsedURL url;
  int           ret;
  op_parsed_url_init(&url);
  ret=op_parse_url_impl(&url,_src);
  if(OP_UNLIKELY(ret<0))op_parsed_url_clear(&url);
  else *_dst=*&url;
  return ret;
}

/*A buffer to hold growing strings.
  The main purpose of this is to consolidate allocation checks and simplify
   cleanup on a failed allocation.*/
struct OpusStringBuf{
  char *buf;
  int   nbuf;
  int   cbuf;
};

static void op_sb_init(OpusStringBuf *_sb){
  _sb->buf=NULL;
  _sb->nbuf=0;
  _sb->cbuf=0;
}

static void op_sb_clear(OpusStringBuf *_sb){
  _ogg_free(_sb->buf);
}

static int op_sb_ensure_capacity(OpusStringBuf *_sb,int _capacity){
  char *buf;
  int   cbuf;
  buf=_sb->buf;
  cbuf=_sb->cbuf;
  if(_capacity>=cbuf-1){
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    if(OP_UNLIKELY(cbuf>INT_MAX-1>>1))return OP_EFAULT;
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    if(OP_UNLIKELY(_capacity>=INT_MAX-1))return OP_EFAULT;
    cbuf=OP_MAX(2*cbuf+1,_capacity+1);
    buf=_ogg_realloc(buf,sizeof(*buf)*cbuf);
    if(OP_UNLIKELY(buf==NULL))return OP_EFAULT;
    _sb->buf=buf;
    _sb->cbuf=cbuf;
  }
  return 0;
}

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static int op_sb_grow(OpusStringBuf *_sb,int _max_size){
  char *buf;
  int   cbuf;
  buf=_sb->buf;
  cbuf=_sb->cbuf;
  OP_ASSERT(_max_size<=INT_MAX-1);
  cbuf=cbuf<=_max_size-1>>1?2*cbuf+1:_max_size+1;
  buf=_ogg_realloc(buf,sizeof(*buf)*cbuf);
  if(OP_UNLIKELY(buf==NULL))return OP_EFAULT;
  _sb->buf=buf;
  _sb->cbuf=cbuf;
  return 0;
}

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static int op_sb_append(OpusStringBuf *_sb,const char *_s,int _len){
  char *buf;
  int   nbuf;
  int   ret;
  nbuf=_sb->nbuf;
  if(OP_UNLIKELY(nbuf>INT_MAX-_len))return OP_EFAULT;
  ret=op_sb_ensure_capacity(_sb,nbuf+_len);
  if(OP_UNLIKELY(ret<0))return ret;
  buf=_sb->buf;
  memcpy(buf+nbuf,_s,sizeof(*buf)*_len);
  nbuf+=_len;
  buf[nbuf]='\0';
  _sb->nbuf=nbuf;
  return 0;
}

static int op_sb_append_string(OpusStringBuf *_sb,const char *_s){
  return op_sb_append(_sb,_s,strlen(_s));
}

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static int op_sb_append_port(OpusStringBuf *_sb,unsigned _port){
  char port_buf[7];
  OP_ASSERT(_port<=65535U);
  sprintf(port_buf,":%u",_port);
  return op_sb_append_string(_sb,port_buf);
}

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static int op_sb_append_nonnegative_int64(OpusStringBuf *_sb,opus_int64 _i){
  char digit;
  int  nbuf_start;
  int  ret;
  OP_ASSERT(_i>=0);
  nbuf_start=_sb->nbuf;
  ret=0;
  do{
    digit='0'+_i%10;
    ret|=op_sb_append(_sb,&digit,1);
    _i/=10;
  }
  while(_i>0);
  if(OP_LIKELY(ret>=0)){
    char *buf;
    int   nbuf_end;
    buf=_sb->buf;
    nbuf_end=_sb->nbuf-1;
    /*We've added the digits backwards.
      Reverse them.*/
    while(nbuf_start<nbuf_end){
      digit=buf[nbuf_start];
      buf[nbuf_start]=buf[nbuf_end];
      buf[nbuf_end]=digit;
      nbuf_start++;
      nbuf_end--;
    }
  }
  return ret;
}

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static struct addrinfo *op_resolve(const char *_host,unsigned _port){
  struct addrinfo *addrs;
  struct addrinfo  hints;
  char             service[6];
  memset(&hints,0,sizeof(hints));
  hints.ai_socktype=SOCK_STREAM;
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#ifndef _WIN32
Timothy B. Terriberry's avatar
Timothy B. Terriberry committed
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  hints.ai_flags=AI_NUMERICSERV;
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#endif
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  OP_ASSERT(_port<=65535U);
  sprintf(service,"%u",_port);
  if(OP_LIKELY(!getaddrinfo(_host,service,&hints,&addrs)))return addrs;
  return NULL;
}

static int op_sock_set_nonblocking(int _fd,int _nonblocking){
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#ifndef _WIN32
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  int flags;
  flags=fcntl(_fd,F_GETFL);
  if(OP_UNLIKELY(flags<0))return flags;
  if(_nonblocking)flags|=O_NONBLOCK;
  else flags&=~O_NONBLOCK;
  return fcntl(_fd,F_SETFL,flags);
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#else
  return IOCTL(_fd, FIONBIO, &_nonblocking);
#endif
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}

/*Disable/enable write coalescing if we can.
  We always send whole requests at once and always parse the response headers
   before sending another one, so normally write coalescing just causes added
   delay.*/
static void op_sock_set_tcp_nodelay(int _fd,int _nodelay){
# if defined(TCP_NODELAY)&&(defined(IPPROTO_TCP)||defined(SOL_TCP))
#  if defined(IPPROTO_TCP)
#   define OP_SO_LEVEL IPPROTO_TCP
#  else
#   define OP_SO_LEVEL SOL_TCP
#  endif
  /*It doesn't really matter if this call fails, but it would be interesting
     to hit a case where it does.*/
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  OP_ALWAYS_TRUE(!SETSOCKOPT(_fd,OP_SO_LEVEL,TCP_NODELAY,
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   &_nodelay,sizeof(_nodelay)));
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# endif
}

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#ifdef _WIN32
static void op_init_winsock(){
  static LONG count = 0;
  static WSADATA wsadata;
  if (InterlockedIncrement(&count) == 1) {
    WSAStartup(0x0202, &wsadata);
  }
}
#endif

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/*A single physical connection to an HTTP server.
  We may have several of these open at once.*/
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struct OpusHTTPConn{
  /*The current position indicator for this connection.*/
  opus_int64    pos;
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  /*The position where the current request will end, or -1 if we're reading
     until EOF (an unseekable stream or the initial HTTP/1.0 request).*/
  opus_int64    end_pos;
  /*The position where next request we've sent will start, or -1 if we haven't
     sent the next request yet.*/
  opus_int64    next_pos;
  /*The end of the next request or -1 if we requested the rest of the resource.
    This is only set to a meaningful value if next_pos is not -1.*/
  opus_int64    next_end;
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  /*The SSL connection, if this is https.*/
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  SSL          *ssl_conn;
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  /*The next connection in either the LRU or free list.*/
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  OpusHTTPConn *next;
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  /*The last time we blocked for reading from this connection.*/
  struct timeb  read_time;
  /*The number of bytes we've read since the last time we blocked.*/
  opus_int64    read_bytes;
  /*The estimated throughput of this connection, in bytes/s.*/
  opus_int64    read_rate;
  /*The socket we're reading from.*/
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  int           fd;
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  /*The number of remaining requests we are allowed on this connection.*/
  int           nrequests_left;
  /*The chunk size to use for pipelining requests.*/
  opus_int32    chunk_size;
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};

static void op_http_conn_init(OpusHTTPConn *_conn){
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  _conn->next_pos=-1;
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  _conn->ssl_conn=NULL;
  _conn->next=NULL;
  _conn->fd=-1;
}

static void op_http_conn_clear(OpusHTTPConn *_conn){
  if(_conn->ssl_conn!=NULL)SSL_free(_conn->ssl_conn);
  /*SSL frees the BIO for us.*/
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  if(_conn->fd!=-1)CLOSE(_conn->fd);
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}

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/*The global stream state.*/
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struct OpusHTTPStream{
  /*The list of connections.*/
  OpusHTTPConn     conns[OP_NCONNS_MAX];
  /*The context object used as a framework for TLS/SSL functions.*/
  SSL_CTX         *ssl_ctx;
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  /*The cached session to reuse for future connections.*/
  SSL_SESSION     *ssl_session;
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  /*The LRU list (ordered from MRU to LRU) of currently connected
     connections.*/
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  OpusHTTPConn    *lru_head;
  /*The free list.*/
  OpusHTTPConn    *free_head;
  /*The URL to connect to.*/
  OpusParsedURL    url;
  /*Information about the address we connected to.*/
  struct addrinfo  addr_info;
  /*The address we connected to.*/
  union{
    struct sockaddr     s;
    struct sockaddr_in  v4;
    struct sockaddr_in6 v6;
  }                addr;
  /*A buffer used to build HTTP requests.*/
  OpusStringBuf    request;
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  /*A buffer used to build proxy CONNECT requests.*/
  OpusStringBuf    proxy_connect;
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  /*A buffer used to receive the response headers.*/
  OpusStringBuf    response;
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  /*The Content-Length, if specified, or -1 otherwise.
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    This will always be specified for seekable streams.*/
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  opus_int64       content_length;
  /*The position indicator used when no connection is active.*/
  opus_int64       pos;
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  /*The connection we're currently reading from.
    This can be -1 if no connection is active.*/
  int              cur_conni;
  /*Whether or not the server supports range requests.*/
  int              seekable;
  /*Whether or not the server supports HTTP/1.1 with persistent connections.*/
  int              pipeline;
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  /*Whether or not we should skip certificate checks.*/
  int              skip_certificate_check;
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  /*The offset of the tail of the request.
    Only the offset in the Range: header appears after this, allowing us to
     quickly edit the request to ask for a new range.*/
  int              request_tail;
  /*The estimated time required to open a new connection, in milliseconds.*/
  opus_int32       connect_rate;
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};

static void op_http_stream_init(OpusHTTPStream *_stream){
  OpusHTTPConn **pnext;
  int ci;
  pnext=&_stream->free_head;
  for(ci=0;ci<OP_NCONNS_MAX;ci++){
    op_http_conn_init(_stream->conns+ci);
    *pnext=_stream->conns+ci;
    pnext=&_stream->conns[ci].next;
  }
  _stream->ssl_ctx=NULL;
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  _stream->ssl_session=NULL;
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  _stream->lru_head=NULL;
  op_parsed_url_init(&_stream->url);
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  op_sb_init(&_stream->request);
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  op_sb_init(&_stream->proxy_connect);
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  op_sb_init(&_stream->response);
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  _stream->seekable=0;
}

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/*Close the connection and move it to the free list.
  _stream:     The stream containing the free list.
  _conn:       The connection to close.
  _penxt:      The linked-list pointer currently pointing to this connection.
  _gracefully: Whether or not to shut down cleanly.*/
static void op_http_conn_close(OpusHTTPStream *_stream,OpusHTTPConn *_conn,
 OpusHTTPConn **_pnext,int _gracefully){
  /*If we don't shut down gracefully, the server MUST NOT re-use our session
     according to RFC 2246, because it can't tell the difference between an
     abrupt close and a truncation attack.
    So we shut down gracefully if we can.
    However, we will not wait if this would block (it's not worth the savings
     from session resumption to do so).
    Clients (that's us) MAY resume a TLS session that ended with an incomplete
     close, according to RFC 2818, so that's no reason to make sure the server
     shut things down gracefully.
    It also says "client implementations MUST treat any premature closes as
     errors and the data received as potentially truncated," but libopusfile
     treats errors and potentially truncated data in unseekable streams just
     like a normal EOF.
    We warn about this in the docs, and give some suggestions if you truly want
     to avoid truncation attacks.*/
  if(_gracefully&&_conn->ssl_conn!=NULL)SSL_shutdown(_conn->ssl_conn);
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  op_http_conn_clear(_conn);
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  _conn->next_pos=-1;
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  _conn->ssl_conn=NULL;
  _conn->fd=-1;
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  OP_ASSERT(*_pnext==_conn);
  *_pnext=_conn->next;
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  _conn->next=_stream->free_head;
  _stream->free_head=_conn;
}

static void op_http_stream_clear(OpusHTTPStream *_stream){
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  while(_stream->lru_head!=NULL){
    op_http_conn_close(_stream,_stream->lru_head,&_stream->lru_head,0);
  }
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  if(_stream->ssl_session!=NULL)SSL_SESSION_free(_stream->ssl_session);
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  if(_stream->ssl_ctx!=NULL)SSL_CTX_free(_stream->ssl_ctx);
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  op_sb_clear(&_stream->response);
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  op_sb_clear(&_stream->proxy_connect);
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  op_sb_clear(&_stream->request);
  op_parsed_url_clear(&_stream->url);
}

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static int op_http_conn_write_fully(OpusHTTPConn *_conn,
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 const char *_buf,int _buf_size){
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  struct pollfd  fd;
  SSL           *ssl_conn;
  fd.fd=_conn->fd;
  ssl_conn=_conn->ssl_conn;
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  while(_buf_size>0){
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    int err;
    if(ssl_conn!=NULL){
      int ret;
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      ret=SSL_write(ssl_conn,_buf,_buf_size);
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      if(ret>0){
        /*Wrote some data.*/
        _buf+=ret;
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        _buf_size-=ret;
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        continue;
      }
      /*Connection closed.*/
      else if(ret==0)return OP_FALSE;
      err=SSL_get_error(ssl_conn,ret);
      /*Yes, renegotiations can cause SSL_write() to block for reading.*/
      if(err==SSL_ERROR_WANT_READ)fd.events=POLLIN;
      else if(err==SSL_ERROR_WANT_WRITE)fd.events=POLLOUT;
      else return OP_FALSE;
    }
    else{
      ssize_t ret;
      errno=0;
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      ret=send(fd.fd,_buf,_buf_size,0);
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      if(ret>0){
        _buf+=ret;
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        _buf_size-=ret;
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        continue;
      }
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      err=ERRNO();
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      if(err!=EAGAIN&&err!=EWOULDBLOCK)return OP_FALSE;
      fd.events=POLLOUT;
    }
    if(poll(&fd,1,OP_POLL_TIMEOUT_MS)<=0)return OP_FALSE;
  }
  return 0;
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}

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static int op_http_conn_estimate_available(OpusHTTPConn *_conn){
  int available;
  int ret;
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  ret=IOCTL(_conn->fd,FIONREAD,&available);
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  if(ret<0)available=0;
  /*This requires the SSL read_ahead flag to be unset to work.
    We ignore partial records as well as the protocol overhead for any pending
     bytes.
    This means we might return somewhat less than can truly be read without
     blocking (if there's a partial record).
    This is okay, because we're using this value to estimate network transfer
     time, and we _have_ already received those bytes.
    We also might return slightly more (due to protocol overhead), but that's
     small enough that it probably doesn't matter.*/
  if(_conn->ssl_conn!=NULL)available+=SSL_pending(_conn->ssl_conn);
  return available;
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}

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static opus_int32 op_time_diff_ms(const struct timeb *_end,
 const struct timeb *_start){
  opus_int64 dtime;
  dtime=_end->time-_start->time;
  OP_ASSERT(_end->millitm<1000);
  OP_ASSERT(_start->millitm<1000);
  if(OP_UNLIKELY(dtime>(0x7FFFFFFF-1000)/1000))return 0x7FFFFFFF;
  if(OP_UNLIKELY(dtime<(-0x7FFFFFFF+999)/1000))return -0x7FFFFFFF-1;
  return (opus_int32)dtime*1000+_end->millitm-_start->millitm;
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}

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/*Update the read rate estimate for this connection.*/
static void op_http_conn_read_rate_update(OpusHTTPConn *_conn){
  struct timeb read_time;
  opus_int32   read_delta_ms;
  opus_int64   read_delta_bytes;
  opus_int64   read_rate;
  read_delta_bytes=_conn->read_bytes;
  if(read_delta_bytes<=0)return;
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  OP_ALWAYS_TRUE(!FTIME(&read_time));
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  read_delta_ms=op_time_diff_ms(&read_time,&_conn->read_time);
  read_rate=_conn->read_rate;
  read_delta_ms=OP_MAX(read_delta_ms,1);
  read_rate+=read_delta_bytes*1000/read_delta_ms-read_rate+4>>3;
  *&_conn->read_time=*&read_time;
  _conn->read_bytes=0;
  _conn->read_rate=read_rate;
}
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/*Tries to read from the given connection.
  [out] _buf: Returns the data read.
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  _buf_size:  The size of the buffer.
  _blocking:  Whether or not to block until some data is retrieved.
  Return: A positive number of bytes read on success.
          0:        The read would block, or the connection was closed.
          OP_EREAD: There was a fatal read error.*/
static int op_http_conn_read(OpusHTTPConn *_conn,
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 char *_buf,int _buf_size,int _blocking){
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  struct pollfd  fd;
  SSL           *ssl_conn;
  int            nread;
  int            nread_unblocked;
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  fd.fd=_conn->fd;
  ssl_conn=_conn->ssl_conn;
  nread=nread_unblocked=0;
  do{
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    int err;
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    if(ssl_conn!=NULL){
      int ret;
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      ret=SSL_read(ssl_conn,_buf+nread,_buf_size-nread);
      OP_ASSERT(ret<=_buf_size-nread);
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      if(ret>0){
        /*Read some data.
          Keep going to see if there's more.*/
        nread+=ret;
        nread_unblocked+=ret;
        continue;
      }
      /*If we already read some data, return it right now.*/
      if(nread>0)break;
      err=SSL_get_error(ssl_conn,ret);
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      if(ret==0){
        /*Connection close.
          Check for a clean shutdown to prevent truncation attacks.
          This check always succeeds for SSLv2, as it has no "close notify"
           message and thus can't verify an orderly shutdown.*/
        return err==SSL_ERROR_ZERO_RETURN?0:OP_EREAD;
      }
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      if(err==SSL_ERROR_WANT_READ)fd.events=POLLIN;
      /*Yes, renegotiations can cause SSL_read() to block for writing.*/
      else if(err==SSL_ERROR_WANT_WRITE)fd.events=POLLOUT;
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      /*Some other error.*/
      else return OP_EREAD;
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    }
    else{
      ssize_t ret;
      errno=0;
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      ret=recv(fd.fd,_buf+nread,_buf_size-nread,0);
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      OP_ASSERT(ret<=_buf_size-nread);
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      if(ret>0){
        /*Read some data.
          Keep going to see if there's more.*/
        nread+=ret;
        nread_unblocked+=ret;
        continue;
      }
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      /*If we already read some data or the connection was closed, return
         right now.*/
      if(ret==0||nread>0)break;
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      err=ERRNO();
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      if(err!=EAGAIN&&err!=EWOULDBLOCK)return OP_EREAD;
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      fd.events=POLLIN;
    }
    _conn->read_bytes+=nread_unblocked;
    op_http_conn_read_rate_update(_conn);
    nread_unblocked=0;
    if(!_blocking)break;
    /*Need to wait to get any data at all.*/
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    if(poll(&fd,1,OP_POLL_TIMEOUT_MS)<=0)return OP_EREAD;
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  }
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  while(nread<_buf_size);
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  _conn->read_bytes+=nread_unblocked;
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  return nread;
}

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/*Tries to look at the pending data for a connection without consuming it.
  [out] _buf: Returns the data at which we're peeking.
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  _buf_size:  The size of the buffer.*/
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static int op_http_conn_peek(OpusHTTPConn *_conn,
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 char *_buf,int _buf_size){
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  struct pollfd   fd;
  SSL            *ssl_conn;
  int             ret;
  fd.fd=_conn->fd;
  ssl_conn=_conn->ssl_conn;
  for(;;){
    int err;
    if(ssl_conn!=NULL){
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      ret=SSL_peek(ssl_conn,_buf,_buf_size);
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      /*Either saw some data or the connection was closed.*/
      if(ret>=0)return ret;
      err=SSL_get_error(ssl_conn,ret);
      if(err==SSL_ERROR_WANT_READ)fd.events=POLLIN;
      /*Yes, renegotiations can cause SSL_peek() to block for writing.*/
      else if(err==SSL_ERROR_WANT_WRITE)fd.events=POLLOUT;
      else return 0;
    }
    else{
      errno=0;
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      ret=(int)recv(fd.fd,_buf,_buf_size,MSG_PEEK);
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      /*Either saw some data or the connection was closed.*/
      if(ret>=0)return ret;
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      err=ERRNO();
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      if(err!=EAGAIN&&err!=EWOULDBLOCK)return 0;
      fd.events=POLLIN;
    }
    /*Need to wait to get any data at all.*/
    if(poll(&fd,1,OP_POLL_TIMEOUT_MS)<=0)return 0;
  }
}

/*When parsing response headers, RFC 2616 mandates that all lines end in CR LF.
  However, even in the year 2012, I have seen broken servers use just a LF.
  This is the evil that Postel's advice from RFC 761 breeds.*/

/*Reads the entirety of a response to an HTTP request into the response buffer.
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  Actual parsing and validation is done later.
  Return: The number of bytes in the response on success, OP_EREAD if the
           connection was closed before reading any data, or another negative
           value on any other error.*/
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static int op_http_conn_read_response(OpusHTTPConn *_conn,
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 OpusStringBuf *_response){
  int ret;
  _response->nbuf=0;
  ret=op_sb_ensure_capacity(_response,OP_RESPONSE_SIZE_MIN);
  if(OP_UNLIKELY(ret<0))return ret;
  for(;;){
    char *buf;
    int   size;
    int   capacity;
    int   read_limit;
    int   terminated;
    size=_response->nbuf;
    capacity=_response->cbuf-1;
    if(OP_UNLIKELY(size>=capacity)){
      ret=op_sb_grow(_response,OP_RESPONSE_SIZE_MAX);
      if(OP_UNLIKELY(ret<0))return ret;
      capacity=_response->cbuf-1;
      /*The response was too large.
        This prevents a bad server from running us out of memory.*/
      if(OP_UNLIKELY(size>=capacity))return OP_EIMPL;
    }
    buf=_response->buf;
    ret=op_http_conn_peek(_conn,buf+size,capacity-size);
    if(OP_UNLIKELY(ret<=0))return size<=0?OP_EREAD:OP_FALSE;
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    /*We read some data.*/
    /*Make sure the starting characters are "HTTP".
      Otherwise we could wind up waiting forever for a response from
       something that is not an HTTP server.*/
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    if(size<4&&op_strncasecmp(buf,"HTTP",OP_MIN(size+ret,4))!=0){
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      return OP_FALSE;
    }
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    /*How far can we read without passing the "\r\n\r\n" terminator?*/
    buf[size+ret]='\0';
    terminated=0;
    for(read_limit=OP_MAX(size-3,0);read_limit<size+ret;read_limit++){
      /*We don't look for the leading '\r' thanks to broken servers.*/
      if(buf[read_limit]=='\n'){
        if(buf[read_limit+1]=='\r'&&OP_LIKELY(buf[read_limit+2]=='\n')){
          terminated=3;
          break;
        }
        /*This case is for broken servers.*/
        else if(OP_UNLIKELY(buf[read_limit+1]=='\n')){
          terminated=2;
          break;
        }
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      }
    }
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    read_limit+=terminated;
    OP_ASSERT(size<=read_limit);
    OP_ASSERT(read_limit<=size+ret);
    /*Actually consume that data.*/
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    ret=op_http_conn_read(_conn,buf+size,read_limit-size,1);
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    if(OP_UNLIKELY(ret<=0))return OP_FALSE;
    size+=ret;
    buf[size]='\0';
    _response->nbuf=size;
    /*We found the terminator and read all the data up to and including it.*/
    if(terminated&&OP_LIKELY(size>=read_limit))return size;
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  }
  return OP_EIMPL;
}

Timothy B. Terriberry's avatar
Timothy B. Terriberry committed
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# define OP_HTTP_DIGIT "0123456789"
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/*The Reason-Phrase is not allowed to contain control characters, except
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   horizontal tab (HT: \011).*/
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# define OP_HTTP_CREASON_PHRASE \
 "\001\002\003\004\005\006\007\010\012\013\014\015\016\017\020\021" \
 "\022\023\024\025\026\027\030\031\032\033\034\035\036\037\177"

# define OP_HTTP_CTLS \
 "\001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020" \
 "\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037\177"

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/*This also includes '\t', but we get that from OP_HTTP_CTLS.*/
# define OP_HTTP_SEPARATORS " \"(),/:;<=>?@[\\]{}"
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/*TEXT can also include LWS, but that has structure, so we parse it
   separately.*/
# define OP_HTTP_CTOKEN OP_HTTP_CTLS OP_HTTP_SEPARATORS

/*Return: The amount of linear white space (LWS) at the start of _s.*/
static int op_http_lwsspn(const char *_s){
  int i;
  for(i=0;;){
    if(_s[0]=='\r'&&_s[1]=='\n'&&(_s[2]=='\t'||_s[2]==' '))i+=3;
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    /*This case is for broken servers.*/
    else if(_s[0]=='\n'&&(_s[1]=='\t'||_s[1]==' '))i+=2;
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    else if(_s[i]=='\t'||_s[i]==' ')i++;
    else return i;
  }
}

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static char *op_http_parse_status_line(int *_v1_1_compat,
 char **_status_code,char *_response){
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  char   *next;
  char   *status_code;
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  int     v1_1_compat;
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  size_t  d;
  /*RFC 2616 Section 6.1 does not say that the tokens in the Status-Line cannot
     be separated by optional LWS, but since it specifically calls out where
     spaces are to be placed and that CR and LF are not allowed except at the
     end, I am assuming this to be true.*/
  /*We already validated that this starts with "HTTP"*/
  OP_ASSERT(op_strncasecmp(_response,"HTTP",4)==0);
  next=_response+4;
  if(OP_UNLIKELY(*next++!='/'))return NULL;
  d=strspn(next,OP_HTTP_DIGIT);
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  /*"Leading zeros MUST be ignored by recipients."*/
  while(*next=='0'){
    next++;
    OP_ASSERT(d>0);
    d--;
  }
  /*We only support version 1.x*/
  if(OP_UNLIKELY(d!=1)||OP_UNLIKELY(*next++!='1'))return NULL;
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  if(OP_UNLIKELY(*next++!='.'))return NULL;
  d=strspn(next,OP_HTTP_DIGIT);
  if(OP_UNLIKELY(d<=0))return NULL;
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  /*"Leading zeros MUST be ignored by recipients."*/
  while(*next=='0'){
    next++;
    OP_ASSERT(d>0);
    d--;
  }
  /*We don't need to parse the version number.
    Any non-zero digit means it's greater than 1.*/
  v1_1_compat=d>0;
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  next+=d;
  if(OP_UNLIKELY(*next++!=' '))return NULL;
  status_code=next;
  d=strspn(next,OP_HTTP_DIGIT);
  if(OP_UNLIKELY(d!=3))return NULL;
  next+=d;
  /*The Reason-Phrase can be empty, but the space must be here.*/
  if(OP_UNLIKELY(*next++!=' '))return NULL;
  next+=strcspn(next,OP_HTTP_CREASON_PHRASE);
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  /*We are not mandating this be present thanks to broken servers.*/
  if(OP_LIKELY(*next=='\r'))next++;
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  if(OP_UNLIKELY(*next++!='\n'))return NULL;
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  if(_v1_1_compat!=NULL)*_v1_1_compat=v1_1_compat;
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  *_status_code=status_code;
  return next;
}

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/*Get the next response header.
  [out] _header: The header token, NUL-terminated, with leading and trailing
                  whitespace stripped, and converted to lower case (to simplify
                  case-insensitive comparisons), or NULL if there are no more
                  response headers.
  [out] _cdr:    The remaining contents of the header, excluding the initial
                  colon (':') and the terminating CRLF ("\r\n"),
                  NUL-terminated, and with leading and trailing whitespace
                  stripped, or NULL if there are no more response headers.
  [inout] _s:    On input, this points to the start of the current line of the
                  response headers.
                 On output, it points to the start of the first line following
                  this header, or NULL if there are no more response headers.
  Return: 0 on success, or a negative value on failure.*/
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static int op_http_get_next_header(char **_header,char **_cdr,char **_s){
  char   *header;
  char   *header_end;
  char   *cdr;
  char   *cdr_end;
  char   *next;
  size_t  d;
  next=*_s;
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  /*The second case is for broken servers.*/
  if(next[0]=='\r'&&next[1]=='\n'||OP_UNLIKELY(next[0]=='\n')){
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    /*No more headers.*/
    *_header=NULL;
    *_cdr=NULL;
    *_s=NULL;
    return 0;
  }
  header=next+op_http_lwsspn(next);
  d=strcspn(header,OP_HTTP_CTOKEN);
  if(OP_UNLIKELY(d<=0))return OP_FALSE;
  header_end=header+d;
  next=header_end+op_http_lwsspn(header_end);
  if(OP_UNLIKELY(*next++!=':'))return OP_FALSE;
  next+=op_http_lwsspn(next);
  cdr=next;
  do{
    cdr_end=next+strcspn(next,OP_HTTP_CTLS);
    next=cdr_end+op_http_lwsspn(cdr_end);
  }
  while(next>cdr_end);
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  /*We are not mandating this be present thanks to broken servers.*/
  if(OP_LIKELY(*next=='\r'))next++;
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  if(OP_UNLIKELY(*next++!='\n'))return OP_FALSE;
  *header_end='\0';
  *cdr_end='\0';
  /*Field names are case-insensitive.*/
  op_string_tolower(header);
  *_header=header;
  *_cdr=cdr;
  *_s=next;
  return 0;
}

static opus_int64 op_http_parse_nonnegative_int64(const char **_next,
 const char *_cdr){
  const char *next;
  opus_int64  content_length;
  int         i;
  next=_cdr+strspn(_cdr,OP_HTTP_DIGIT);
  *_next=next;
  if(OP_UNLIKELY(next<=_cdr))return OP_FALSE;
  while(*_cdr=='0')_cdr++;
  if(OP_UNLIKELY(next-_cdr>19))return OP_EIMPL;
  content_length=0;
  for(i=0;i<next-_cdr;i++){
    int digit;
    digit=_cdr[i]-'0';
    /*Check for overflow.*/
    if(OP_UNLIKELY(content_length>(OP_INT64_MAX-9)/10+(digit<=7))){
      return OP_EIMPL;
    }
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    content_length=content_length*10+digit;
  }
  return content_length;
}

static opus_int64 op_http_parse_content_length(const char *_cdr){
  const char *next;
  opus_int64  content_length;
  content_length=op_http_parse_nonnegative_int64(&next,_cdr);
  if(OP_UNLIKELY(*next!='\0'))return OP_FALSE;
  return content_length;
}

static int op_http_parse_content_range(opus_int64 *_first,opus_int64 *_last,
 opus_int64 *_length,const char *_cdr){
  opus_int64 first;
  opus_int64 last;
  opus_int64 length;
  size_t     d;
  if(OP_UNLIKELY(op_strncasecmp(_cdr,"bytes",5)!=0))return OP_FALSE;
  _cdr+=5;
  d=op_http_lwsspn(_cdr);
  if(OP_UNLIKELY(d<=0))return OP_FALSE;
  _cdr+=d;
  if(*_cdr!='*'){
    first=op_http_parse_nonnegative_int64(&_cdr,_cdr);
    if(OP_UNLIKELY(first<0))return (int)first;
    _cdr+=op_http_lwsspn(_cdr);
    if(*_cdr++!='-')return OP_FALSE;
    _cdr+=op_http_lwsspn(_cdr);
    last=op_http_parse_nonnegative_int64(&_cdr,_cdr);
    if(OP_UNLIKELY(last<0))return (int)last;
    _cdr+=op_http_lwsspn(_cdr);
  }
  else{
    /*This is for a 416 response (Requested range not satisfiable).*/
    first=last=-1;
    _cdr++;
  }
  if(OP_UNLIKELY(*_cdr++!='/'))return OP_FALSE;
  if(*_cdr!='*'){
    length=op_http_parse_nonnegative_int64(&_cdr,_cdr);
    if(OP_UNLIKELY(length<0))return (int)length;
  }
  else{
    /*The total length is unspecified.*/
    _cdr++;
    length=-1;
  }
  if(OP_UNLIKELY(*_cdr!='\0'))return OP_FALSE;
  if(OP_UNLIKELY(last<first))return OP_FALSE;
  if(length>=0&&OP_UNLIKELY(last>=length))return OP_FALSE;
  *_first=first;
  *_last=last;
  *_length=length;
  return 0;
}

/*Parse the Connection response header and look for a "close" token.
  Return: 1 if a "close" token is found, 0 if it's not found, and a negative
           value on error.*/
static int op_http_parse_connection(char *_cdr){
  size_t d;
  int    ret;
  ret=0;
  for(;;){
    d=strcspn(_cdr,OP_HTTP_CTOKEN);
    if(OP_UNLIKELY(d<=0))return OP_FALSE;
    if(op_strncasecmp(_cdr,"close",(int)d)==0)ret=1;
    /*We're supposed to strip and ignore any headers mentioned in the
       Connection header if this response is from an HTTP/1.0 server (to
       work around forwarding of hop-by-hop headers by old proxies), but the
       only hop-by-hop header we look at is Connection itself.
      Everything else is a well-defined end-to-end header, and going back and
       undoing the things we did based on already-examined headers would be
       hard (since we only scan them once, in a destructive manner).
      Therefore we just ignore all the other tokens.*/
    _cdr+=d;
    d=op_http_lwsspn(_cdr);
    if(d<=0)break;
    _cdr+=d;
  }
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  return OP_UNLIKELY(*_cdr!='\0')?OP_FALSE:ret;
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