http.c 55.6 KB
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#include "internal.h"
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <string.h>

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;
  ret=(char *)_ogg_malloc(sizeof(*ret)*(len+1));
  memcpy(ret,_start,sizeof(*ret)*(len));
  ret[len]='\0';
  return ret;
}

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

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

#define OP_URL_IS_DEFAULT_PORT(_url) \
 (!OP_URL_IS_SSL(_url)&&(_url)->port==80 \
 ||OP_URL_IS_SSL(_url)&&(_url)->port==443)

/*URI character classes (from RFC 3986).*/
#define OP_URL_ALPHA \
 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
#define OP_URL_DIGIT       "01234567890"
#define OP_URL_HEXDIGIT    "01234567890ABCDEFabcdef"
/*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;
    const char *host_end;
    char        host_buf[28];
    /*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.*/
    if(OP_LIKELY(*host!='/'))path=host;
    /*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);
    /*Some other host: give up.*/
    if(OP_UNLIKELY(op_strncasecmp(host_buf,"localhost",9)!=0))return NULL;
    path=host_end;
  }
  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)
# include <sys/types.h>
# include <sys/socket.h>
# include <sys/time.h>
# include <arpa/inet.h>
# include <fcntl.h>
# include <netinet/in.h>
# include <netdb.h>
# include <poll.h>
# include <unistd.h>
# include <openssl/ssl.h>

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;
}

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.
  It is meant to be RFC 3986-compliant.*/
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  *fragment_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{
    user=NULL;
    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/>.*/
  if(*path_end=='#'){
    uri_end=fragment_end=path_end+1+strspn(path_end+1,OP_URL_QUERY_FRAG);
  }
  else uri_end=path_end;
  /*If there's anything left, this was not a valid URL.*/
  if(OP_UNLIKELY(*path_end!='\0'))return OP_EINVAL;
  _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){
    if(OP_UNLIKELY(cbuf>=INT_MAX-1>>1))return OP_EFAULT;
    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;
}

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));
}

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;
}

struct OpusHTTPConn{
  /*The current position indicator for this connection.*/
  opus_int64    pos;
  SSL          *ssl_conn;
  OpusHTTPConn *next;
  int           fd;
};

static void op_http_conn_init(OpusHTTPConn *_conn){
  _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.*/
  if(_conn->fd!=-1)close(_conn->fd);
}

/*The maximum number of simultaneous connections.
  RFC 2616 says this SHOULD NOT be more than 2, but everyone on the modern web
   ignores that.
  If it makes you feel better, we'll only ever be reading from one of these at
   a time; the others are kept around mainly to avoid slow-starting a new
   connection if we seek back near somewhere we were reading before.*/
# define OP_NCONNS_MAX (4)

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;
  /*The LRU list (ordered from MRU to LRU) of connections.*/
  OpusHTTPConn    *lru_head;
  /*The free list.*/
  OpusHTTPConn    *free_head;
  /*The URL to connect to.*/
  OpusParsedURL    url;
  /*The connection we're currently reading from.
    This can be -1 if no connection is active.*/
  int              cur_conni;
  /*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;
  /*The offset of the tail of the request.
    Only the offset in the Range: header appears after this.*/
  int              request_tail;
  /*Whether or not the server supports range requests.*/
  int              seekable;
  /*The Content-Length, if specified, or -1 otherwise.
    This will always be valid for seekable streams.*/
  opus_int64       content_length;
  /*The position indicator used when no connection is active.*/
  opus_int64       pos;
};

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;
517 518
  _stream->lru_head=NULL;
  op_parsed_url_init(&_stream->url);
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  op_sb_init(&_stream->request);
  _stream->seekable=0;
}

/*Close the connection at the top of the LRU list.*/
static void op_http_conn_close(OpusHTTPStream *_stream,OpusHTTPConn *_conn){
  op_http_conn_clear(_conn);
  _conn->ssl_conn=NULL;
  _conn->fd=-1;
  OP_ASSERT(_stream->lru_head==_conn);
  _stream->lru_head=_conn->next;
  _conn->next=_stream->free_head;
  _stream->free_head=_conn;
}

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

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;
  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){
  int flags;
  flags=fcntl(_fd,F_GETFL);
  if(OP_UNLIKELY(flags==-1))return flags;
  if(_nonblocking)flags|=O_NONBLOCK;
  else flags&=~O_NONBLOCK;
  return fcntl(_fd,F_SETFL,flags);
}

/*Try to start a connection to the next address in the given list of a given
   type.
  _fd:         The socket to connect with.
  [out] _addr: A pointer to the list of addresses.
               This will be advanced to the first one that matches the given
                address family (possibly the current one).
  _ai_family:  The address family to connect to.
  Return: 1        If the connection was successful.
          0        If the connection is in progress.
          OP_FALSE If the connection failed and there were no more addresses
                    left to try.
                    *_addr will be set to NULL in this case.*/
static int op_sock_connect_next(int _fd,
 struct addrinfo **_addr,int _ai_family){
  struct addrinfo *addr;
  addr=*_addr;
  for(;;){
    /*Move to the next address of the requested type.*/
    for(;addr!=NULL&&addr->ai_family!=_ai_family;addr=addr->ai_next);
    *_addr=addr;
    /*No more: failure.*/
    if(addr==NULL)return OP_FALSE;
    if(connect(_fd,addr->ai_addr,addr->ai_addrlen)!=-1)return 1;
    if(OP_LIKELY(errno==EINPROGRESS))return 0;
  }
}

typedef int (*op_ssl_step_func)(SSL *_ssl_conn);

/*Try to run an SSL function to completion (blocking if necessary).*/
static int op_do_ssl_step(SSL *_ssl_conn,int _fd,op_ssl_step_func _step){
  struct pollfd fd;
  fd.fd=_fd;
  for(;;){
    int ret;
    int err;
    ret=(*_step)(_ssl_conn);
    if(ret>=0)return ret;
    err=SSL_get_error(_ssl_conn,ret);
    if(err==SSL_ERROR_WANT_READ)fd.events=POLLIN;
    else if(err==SSL_ERROR_WANT_WRITE)fd.events=POLLOUT;
    else return OP_FALSE;
    if(poll(&fd,1,-1)==-1)return OP_FALSE;
  }
}

/*The number of address families to try connecting to simultaneously.*/
# define OP_NPROTOS (2)

static int op_http_connect(OpusHTTPStream *_stream,OpusHTTPConn *_conn,
 struct addrinfo *_addrs){
  struct addrinfo *addr;
  struct addrinfo *addrs[OP_NPROTOS];
  struct pollfd    fds[OP_NPROTOS];
  int              ai_family;
  int              nprotos;
  int              ret;
  int              pi;
  int              pj;
  for(pi=0;pi<OP_NPROTOS;pi++)addrs[pi]=NULL;
  addr=_addrs;
  /*Try connecting via both IPv4 and IPv6 simultaneously, and keep the first
     one that succeeds.*/
  for(;addr!=NULL;addr=addr->ai_next){
    /*Give IPv6 a slight edge by putting it first in the list.*/
    if(addr->ai_family==AF_INET6){
      OP_ASSERT(addr->ai_addrlen<=sizeof(struct sockaddr_in6));
      if(addrs[0]==NULL)addrs[0]=addr;
    }
    else if(addr->ai_family==AF_INET){
      OP_ASSERT(addr->ai_addrlen<=sizeof(struct sockaddr_in));
      if(addrs[1]==NULL)addrs[1]=addr;
    }
  }
  /*Consolidate the list of addresses.*/
  for(pi=nprotos=0;pi<OP_NPROTOS;pi++){
    if(addrs[pi]!=NULL){
      addrs[nprotos]=addrs[pi];
      nprotos++;
    }
  }
  /*Try to start a connection to each protocol.*/
  for(pi=0;pi<nprotos;pi++){
    ai_family=addrs[pi]->ai_family;
    fds[pi].fd=socket(ai_family,SOCK_STREAM,addrs[pi]->ai_protocol);
    fds[pi].events=POLLOUT;
    if(OP_LIKELY(fds[pi].fd!=-1)){
      if(OP_LIKELY(op_sock_set_nonblocking(fds[pi].fd,1)!=-1)){
        ret=op_sock_connect_next(fds[pi].fd,addrs+pi,ai_family);
        if(ret>1){
          /*It succeeded right away, so stop.*/
          nprotos=pi+1;
          break;
        }
        /*Otherwise go on to the next protocol, and skip the clean-up below.*/
        else if(ret==0)continue;
        /*Tried all the addresses for this protocol.*/
      }
      /*Clean up the socket.*/
      close(fds[pi].fd);
    }
    /*Remove this protocol from the list.*/
    memmove(addrs+pi,addrs+pi+1,sizeof(*addrs)*(nprotos-pi-1));
    nprotos--;
    pi--;
  }
  /*Wait for one of the connections to finish.*/
  while(pi>=nprotos&&nprotos>0&&poll(fds,nprotos,-1)!=-1){
    for(pi=0;pi<nprotos;pi++){
      socklen_t errlen;
      int       err;
      /*Still waiting...*/
      if(!fds[pi].revents)continue;
      errlen=sizeof(err);
      if(getsockopt(fds[pi].fd,SOL_SOCKET,SO_ERROR,&err,&errlen)!=-1&&err==0){
        /*Success!*/
        break;
      }
      /*Move on to the next address for this protocol.*/
      ai_family=addrs[pi]->ai_family;
      addrs[pi]=addrs[pi]->ai_next;
      ret=op_sock_connect_next(fds[pi].fd,addrs+pi,ai_family);
      /*It succeeded right away, so stop.*/
      if(ret>0)break;
      /*Otherwise go on to the next protocol, and skip the clean-up below.*/
      else if(ret==0)continue;
      /*Tried all the addresses for this protocol.
        Remove it from the list.*/
      close(fds[pi].fd);
      memmove(fds+pi,fds+pi+1,sizeof(*fds)*(nprotos-pi-1));
      memmove(addrs+pi,addrs+pi+1,sizeof(*addrs)*(nprotos-pi-1));
      nprotos--;
      pi--;
    }
  }
  /*Close all the other sockets.*/
  for(pj=0;pj<nprotos;pj++)if(pi!=pj)close(fds[pj].fd);
  /*If none of them succeeded, we're done.*/
  if(pi>=nprotos)return OP_FALSE;
  /*Save this address for future connection attempts.*/
  if(addrs[pi]!=&_stream->addr_info){
    memcpy(&_stream->addr_info,addrs[pi],sizeof(_stream->addr_info));
    _stream->addr_info.ai_addr=&_stream->addr.s;
    _stream->addr_info.ai_next=NULL;
    memcpy(&_stream->addr,addrs[pi]->ai_addr,addrs[pi]->ai_addrlen);
  }
  if(OP_URL_IS_SSL(&_stream->url)){
    SSL *ssl_conn;
    BIO *ssl_bio;
    /*Start the SSL connection.*/
    OP_ASSERT(_stream->ssl_ctx!=NULL);
    ssl_conn=SSL_new(_stream->ssl_ctx);
    if(OP_LIKELY(ssl_conn!=NULL)){
      ssl_bio=BIO_new_socket(fds[pi].fd,BIO_NOCLOSE);
      if(OP_LIKELY(ssl_bio!=NULL)){
        SSL_set_bio(ssl_conn,ssl_bio,ssl_bio);
        SSL_set_connect_state(ssl_conn);
        ret=op_do_ssl_step(ssl_conn,fds[pi].fd,SSL_connect);
        if(OP_LIKELY(ret>0)){
          ret=op_do_ssl_step(ssl_conn,fds[pi].fd,SSL_do_handshake);
          if(OP_LIKELY(ret>0)){
            _conn->ssl_conn=ssl_conn;
            _conn->fd=fds[pi].fd;
            return 0;
          }
        }
        /*If we wanted to shut down cleanly, we would do:
        op_do_ssl_step(ssl_conn,fds[pi].fd,SSL_shutdown);*/
      }
      SSL_free(ssl_conn);
    }
    close(fds[pi].fd);
    return OP_FALSE;
  }
  /*Just a normal non-SSL connection.*/
  _conn->ssl_conn=NULL;
  _conn->fd=fds[pi].fd;
  return 0;
}

# define OP_BASE64_LENGTH(_len) (((_len)+2)/3*4)

static const char BASE64_TABLE[64]={
  'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P',
  'Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f',
  'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v',
  'w','x','y','z','0','1','2','3','4','5','6','7','8','9','+','/'
};

static char *op_base64_encode(char *_dst,const char *_src,int _len){
  unsigned s0;
  unsigned s1;
  unsigned s2;
  int      ngroups;
  int      i;
  ngroups=_len/3;
  for(i=0;i<ngroups;i++){
    s0=_src[3*i+0];
    s1=_src[3*i+1];
    s2=_src[3*i+2];
    _dst[4*i+0]=BASE64_TABLE[s0>>2];
    _dst[4*i+1]=BASE64_TABLE[s0&3<<4|s1>>4];
    _dst[4*i+2]=BASE64_TABLE[s1&15<<2|s2>>6];
    _dst[4*i+3]=BASE64_TABLE[s2&63];
  }
  _len-=3*i;
  if(_len==1){
    s0=_src[3*i+0];
    _dst[4*i+0]=BASE64_TABLE[s0>>2];
    _dst[4*i+1]=BASE64_TABLE[s0&3<<4];
    _dst[4*i+2]='=';
    _dst[4*i+3]='=';
    i++;
  }
  else if(_len==2){
    s0=_src[3*i+0];
    s1=_src[3*i+1];
    _dst[4*i+0]=BASE64_TABLE[s0>>2];
    _dst[4*i+1]=BASE64_TABLE[s0&3<<4|s1>>4];
    _dst[4*i+2]=BASE64_TABLE[s1&15<<2];
    _dst[4*i+3]='=';
    i++;
  }
  _dst[4*i]='\0';
  return _dst+4*i;
}

/*Construct an HTTP authorization header using RFC 2617's Basic Authentication
   Scheme and append it to the given string buffer.*/
static int op_sb_append_basic_auth_header(OpusStringBuf *_sb,
 const char *_header,const char *_user,const char *_pass){
  int user_len;
  int pass_len;
  int user_pass_len;
  int base64_len;
  int nbuf_total;
  int ret;
  ret=op_sb_append_string(_sb,_header);
  ret|=op_sb_append(_sb,": Basic ",8);
  user_len=strlen(_user);
  pass_len=strlen(_pass);
  if(OP_UNLIKELY(pass_len>INT_MAX-user_len))return OP_EFAULT;
  if(OP_UNLIKELY(user_len+pass_len>(INT_MAX>>2)*3-3))return OP_EFAULT;
  user_pass_len=user_len+1+pass_len;
  base64_len=OP_BASE64_LENGTH(user_pass_len);
  /*Stick "user:pass" at the end of the buffer so we can Base64 encode it
     in-place.*/
  nbuf_total=_sb->nbuf;
  if(OP_UNLIKELY(base64_len>INT_MAX-nbuf_total))return OP_EFAULT;
  nbuf_total+=base64_len;
  ret|=op_sb_ensure_capacity(_sb,nbuf_total);
  if(OP_UNLIKELY(ret<0))return ret;
  _sb->nbuf=nbuf_total-user_pass_len;
  ret=op_sb_append(_sb,_user,user_len);
  OP_ASSERT(!ret);
  ret=op_sb_append(_sb,":",1);
  OP_ASSERT(!ret);
  ret=op_sb_append(_sb,_pass,pass_len);
  OP_ASSERT(!ret);
  op_base64_encode(_sb->buf+nbuf_total-base64_len,
   _sb->buf+nbuf_total-user_pass_len,user_pass_len);
  return op_sb_append(_sb,"\r\n",2);
}

static int op_http_conn_write_fully(OpusHTTPConn *_conn,
 const char *_buf,int _size){
  struct pollfd  fd;
  SSL           *ssl_conn;
  fd.fd=_conn->fd;
  ssl_conn=_conn->ssl_conn;
  while(_size>0){
    int err;
    if(ssl_conn!=NULL){
      int ret;
      ret=SSL_write(ssl_conn,_buf,_size);
      if(ret>0){
        /*Wrote some data.*/
        _buf+=ret;
        _size-=ret;
        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;
      ret=write(fd.fd,_buf,_size);
      if(ret>0){
        _buf+=ret;
        _size-=ret;
        continue;
      }
      err=errno;
      if(err!=EAGAIN&&err!=EWOULDBLOCK)return OP_FALSE;
      fd.events=POLLOUT;
    }
    if(poll(&fd,1,-1)==-1)return OP_FALSE;
  }
  return 0;
}

/*Tries to read from the given connection.
  [out] _buf: Returns the data read.
  _size:      The size of the buffer.
  _block      Whether or not to block until some data is retrieved.*/
static ptrdiff_t op_http_conn_read(OpusHTTPConn *_conn,
 char *_buf,ptrdiff_t _size,int _block){
  struct pollfd   fd;
  SSL            *ssl_conn;
  ptrdiff_t       nread;
  fd.fd=_conn->fd;
  ssl_conn=_conn->ssl_conn;
  nread=0;
  do{
    int err;
    if(ssl_conn!=NULL){
      int ret;
      ret=SSL_read(ssl_conn,_buf+nread,_size-nread);
      if(ret>0){
        /*Read some data.
          Keep going to see if there's more.*/
        nread+=ret;
        continue;
      }
      /*Connection closed.*/
      else if(ret==0)break;
      /*If we already read some data, return it right now.*/
      if(nread>0)break;
      err=SSL_get_error(ssl_conn,ret);
      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;
      else return 0;
    }
    else{
      ssize_t ret;
      errno=0;
      ret=read(fd.fd,_buf+nread,_size-nread);
      if(ret>0){
        /*Read some data.
          Keep going to see if there's more.*/
        nread+=ret;
        continue;
      }
      /*If we already read some data, return it right now.*/
      if(nread>0)break;
      err=errno;
      if(err!=EAGAIN&&err!=EWOULDBLOCK)return 0;
      fd.events=POLLIN;
    }
    if(!_block)break;
    /*Need to wait to get any data at all.*/
    if(poll(&fd,1,-1)==-1)return 0;
  }
  while(nread<_size);
  return nread;
}

/*Reads the entirety of a response to an HTTP request into a buffer.
  Actual parsing and validation is done later.*/
static int op_http_conn_read_response(OpusHTTPConn *_conn,
 char *_buf,int _size){
  /*The remaining size of the buffer.*/
  int size;
  /*How many characters we've yet to see from the "\r\n\r\n" terminator.*/
  int state;
  size=_size;
  state=4;
  while(size>=state){
    ptrdiff_t ret;
    int       len;
    ret=op_http_conn_read(_conn,_buf,state,1);
    if(ret<=0)return OP_FALSE;
    /*We read some data.*/
    _buf+=ret;
    size-=ret;
    len=_size-size;
    /*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.*/
    if(len-ret<4&&op_strncasecmp(_buf-len,"HTTP",OP_MIN(len,4))!=0){
      return OP_FALSE;
    }
    /*How far along on the "\r\n\r\n" terminator are we?*/
    if(*(_buf-1)=='\n'){
      if(len>=2&&*(_buf-2)=='\r'){
        if(len>=4&&*(_buf-3)=='\n'&&*(_buf-4)=='\r')return len;
        state=2;
      }
      else state=4;
    }
    else if(*(_buf-1)=='\r'){
      state=3;
      if(len>=3&&*(_buf-2)=='\n'&&*(_buf-3)=='\r')state=1;
    }
    else state=4;
  }
  /*Not enough space left in the buffer to add the characters we'd need to get
     a valid terminator.*/
  return OP_EIMPL;
}

/*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)

/*The maximum size of a response message (before the body).
  Responses larger than this will be discarded.*/
# define OP_RESPONSE_SIZE_MAX (1024)

# define OP_HTTP_DIGIT "01234567890"

/*The Reason-Phrase is not allowed to contain control characters, except
   horizontal tab (HT).*/
# 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"

/*These also include ' ' and '\t', but we get those from CTLS.*/
# define OP_HTTP_SEPARATORS "\"(),/:;<=>?@[\\]{}"

/*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;
    else if(_s[i]=='\t'||_s[i]==' ')i++;
    else return i;
  }
}

static char *op_http_parse_status_line(char **_status_code,char *_response){
  char   *next;
  char   *status_code;
  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);
  if(OP_UNLIKELY(d<=0))return NULL;
  next+=d;
  if(OP_UNLIKELY(*next++!='.'))return NULL;
  d=strspn(next,OP_HTTP_DIGIT);
  if(OP_UNLIKELY(d<=0))return NULL;
  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);
  if(OP_UNLIKELY(*next++!='\r'))return NULL;
  if(OP_UNLIKELY(*next++!='\n'))return NULL;
  *_status_code=status_code;
  return next;
}

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;
  if(next[0]=='\r'&&next[1]=='\n'){
    /*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);
  if(OP_UNLIKELY(*next++!='\r'))return OP_FALSE;
  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;
    }
    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!=-1&&OP_UNLIKELY(last>=length))return OP_FALSE;
  *_first=first;
  *_last=last;
  *_length=length;
  return 0;
}

static int op_http_stream_open(OpusHTTPStream *_stream,const char *_url,
 int _flags,const char *_proxy_host,unsigned _proxy_port,
 const char *_proxy_user,const char *_proxy_pass){
  struct addrinfo *addrs;
  const char      *last_host;
  unsigned         last_port;
  int              nredirs;
  int              ret;
  if(_proxy_host!=NULL&&OP_UNLIKELY(_proxy_port>65535U))return OP_EINVAL;
  last_host=NULL;
  ret=op_parse_url(&_stream->url,_url);
  if(OP_UNLIKELY(ret<0))return ret;
  for(nredirs=0;nredirs<OP_REDIRECT_LIMIT;nredirs++){
    char        response[OP_RESPONSE_SIZE_MAX];
    char       *next;
    char       *status_code;
    const char *host;
    unsigned    port;
    if(_proxy_host==NULL){
      host=_stream->url.host;
      port=_stream->url.port;
    }
    else{
      host=_proxy_host;
      port=_proxy_port;
    }
    /*If connecting to the same place as last time, don't re-resolve it.*/
    addrs=NULL;
    if(last_host!=NULL){
      if(strcmp(last_host,host)==0&&last_port==port)addrs=&_stream->addr_info;
      if(last_host!=_proxy_host)_ogg_free((void *)last_host);
    }
    last_host=host;
    last_port=port;
    /*Initialize the SSL library if necessary.*/
1194
    if(OP_URL_IS_SSL(&_stream->url)&&_stream->ssl_ctx==NULL){
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      SSL_CTX *ssl_ctx;
      /*We need to establish a CONNECT tunnel to handle https proxying.
        This isn't supported yet.*/
      if(_proxy_host!=NULL)return OP_EIMPL;
      /*TODO: The documentation says this is not re-entrant.*/
      SSL_library_init();
      /*Needed to get SHA2 algorithms with old OpenSSL versions.*/
      OpenSSL_add_ssl_algorithms();
      ssl_ctx=SSL_CTX_new(SSLv23_client_method());
      if(ssl_ctx==NULL)return OP_EFAULT;
      if(!(_flags&OP_SSL_SKIP_CERTIFICATE_CHECK)){
        SSL_CTX_set_verify(ssl_ctx,SSL_VERIFY_PEER,NULL);
      }
      _stream->ssl_ctx=ssl_ctx;
    }
    /*Pop connection 0 off the free list and put it on the LRU list.*/
    OP_ASSERT(_stream->free_head==_stream->conns+0);
    _stream->lru_head=_stream->conns+0;
    _stream->free_head=_stream->conns[0].next;
    _stream->conns[0].next=NULL;
    /*Actually make the connection.*/
    if(addrs!=&_stream->addr_info){
      addrs=op_resolve(host,port);
      if(OP_UNLIKELY(addrs==NULL))return OP_FALSE;
    }
    ret=op_http_connect(_stream,_stream->conns+0,addrs);
    if(addrs!=&_stream->addr_info)freeaddrinfo(addrs);
    if(OP_UNLIKELY(ret<0))return ret;
    /*Build the request to send.*/
    _stream->request.nbuf=0;
    ret=op_sb_append(&_stream->request,"GET ",4);
    ret|=op_sb_append_string(&_stream->request,
     _proxy_host!=NULL?_url:_stream->url.path);
    ret|=op_sb_append(&_stream->request," HTTP/1.0\r\n",11);
    ret|=op_sb_append(&_stream->request,"Host: ",6);
    ret|=op_sb_append_string(&_stream->request,_stream->url.host);
    if(!OP_URL_IS_DEFAULT_PORT(&_stream->url)){
      char port[7];
      OP_ASSERT(_stream->url.port<=65535U);
      sprintf(port,":%u",_stream->url.port);
      ret|=op_sb_append_string(&_stream->request,port);
    }
    ret|=op_sb_append(&_stream->request,"\r\n",2);
    /*User-Agents have been a bad idea, so send as little as possible.
      RFC 2616 requires at least one token in the User-Agent, which must have
       at least one character.*/
    ret|=op_sb_append(&_stream->request,"User-Agent: .\r\n",15);
    if(_proxy_host!=NULL&&_proxy_user!=NULL&&_proxy_pass!=NULL){
      ret|=op_sb_append_basic_auth_header(&_stream->request,
       "Proxy-Authorization",_proxy_user,_proxy_pass);
    }
    if(_stream->url.user!=NULL&&_stream->url.pass!=NULL){
      ret|=op_sb_append_basic_auth_header(&_stream->request,
       "Authorization",_stream->url.user,_stream->url.pass);
    }
    /*Always send a Referer [sic] header.
      It's common to refuse to serve a resource unless one is present.
      We just use the relative "/" URI to suggest we came from the same domain,
       as this is the most common check.
      This might violate RFC 2616's mandate that the field "MUST NOT be sent if
       the Request-URI was obtained from a source that does not have its own
       URI, such as input from the user keyboard," but we don't really have any
       way to know.*/
    /*TODO: Should we update this on redirects?*/
    ret|=op_sb_append(&_stream->request,"Referer: /\r\n",12);
    /*Always send a Range request header to find out if we're seekable.*/
    ret|=op_sb_append(&_stream->request,"Range: bytes=0-\r\n",17);
    /*Remember where this is so we can append offsets to it later.*/
    _stream->request_tail=_stream->request.nbuf-4;
    ret|=op_sb_append(&_stream->request,"\r\n",2);
    if(OP_UNLIKELY(ret<0))return ret;
    ret=op_http_conn_write_fully(_stream->conns+0,
     _stream->request.buf,_stream->request.nbuf);
    if(OP_UNLIKELY(ret<0))return ret;
    ret=op_http_conn_read_response(_stream->conns+0,
     response,sizeof(response)/sizeof(*response));
    if(OP_UNLIKELY(ret<0))return ret;
    next=op_http_parse_status_line(&status_code,response);
    if(next==NULL)return OP_FALSE;
    if(status_code[0]=='2'){
      opus_int64 content_length;
      opus_int64 range_length;
      /*We only understand 20x codes.*/
      if(status_code[1]!='0')return OP_FALSE;
      content_length=-1;
      range_length=-1;
      for(;;){
        char *header;
        char *cdr;
        ret=op_http_get_next_header(&header,&cdr,&next);
        if(OP_UNLIKELY(ret<0))return ret;
        if(header==NULL)break;
        if(strcmp(header,"content-length")==0){
          /*Two Content-Length headers?*/
          if(OP_UNLIKELY(content_length!=-1))return OP_FALSE;
          content_length=op_http_parse_content_length(cdr);
          if(OP_UNLIKELY(content_length<0))return (int)content_length;
          /*Make sure the Content-Length and Content-Range headers match.*/
          if(range_length!=-1&&OP_UNLIKELY(content_length!=range_length)){
            return OP_FALSE;
          }
        }
        else if(strcmp(header,"content-range")==0){
          opus_int64 range_first;
          opus_int64 range_last;
          /*Two Content-Range headers?*/
          if(OP_UNLIKELY(range_length!=-1))return OP_FALSE;
          ret=op_http_parse_content_range(&range_first,&range_last,
           &range_length,cdr);
          if(OP_UNLIKELY(ret<0))return ret;
          /*"A response with satus code 206 (Partial Content) MUST NOTE
             include a Content-Range field with a byte-range-resp-spec of
             '*'."*/
          if(status_code[2]=='6'
           &&(OP_UNLIKELY(range_first<0)||OP_UNLIKELY(range_last<0))){
            return OP_FALSE;
          }
          /*We asked for the entire resource.*/
          if(range_length>=0){
            /*Quit if we didn't get it.*/
            if(range_last>=0&&OP_UNLIKELY(range_last!=range_length-1)){
              return OP_FALSE;
            }
          }
          /*If there was no length, use the end of the range.*/
          else if(range_last>=0)range_length=range_last+1;
          /*Make sure the Content-Length and Content-Range headers match.*/
          if(content_length!=-1&&OP_UNLIKELY(content_length!=range_length)){
            return OP_FALSE;
          }
        }
      }
      switch(status_code[2]){
        /*200 OK*/
        case '0':break;
        /*203 Non-Authoritative Information*/
        case '3':break;
        /*204 No Content*/
        case '4':{
          if(content_length!=-1&&OP_UNLIKELY(content_length!=0)){
            return OP_FALSE;
          }
        }break;
        /*206 Partial Content*/
        case '6':{
          /*No Content-Range header.*/
          if(OP_UNLIKELY(range_length==-1))return OP_FALSE;
          content_length=range_length;
          /*The server supports range requests for this resource.
            We can seek.*/
          _stream->seekable=1;
        }break;
        /*201 Created: the response "SHOULD include an entity containing a list
           of resource characteristics and location(s)," but not an Opus file.
          202 Accepted: the response "SHOULD include an indication of request's
           current status and either a pointer to a status monitor or some
           estimate of when the user can expect the request to be fulfilled,"
           but not an Opus file.
          205 Reset Content: this "MUST NOT include an entity," meaning no Opus
           file.
          207...209 are not yet defined, so we don't know how to handle them.*/
        default:return OP_FALSE;
      }
      _stream->content_length=content_length;
      _stream->conns[0].pos=0;
      _stream->cur_conni=0;
      /*The URL has been successfully opened.*/
      return 0;
    }
    /*Shouldn't get 1xx; 4xx and 5xx are both failures (and we don't retry).
      Everything else is undefined.*/
    else if(status_code[0]!='3')return OP_FALSE;
    /*We have some form of redirect request.*/
    /*We only understand 30x codes.*/
    if(status_code[1]!='0')return OP_FALSE;
    switch(status_code[2]){
      /*300 Multiple Choices: "If the server has a preferred choice of
         representation, it SHOULD include the specific URI for that
         representation in the Location field," otherwise we'll fail.*/
      case '0':
      /*301 Moved Permanently*/
      case '1':
      /*302 Found*/
      case '2':
      /*307 Temporary Redirect*/
      case '7':break;
      /*305 Use Proxy: "The Location field gives the URI of the proxy."
        TODO: This shouldn't actually be that hard to do.*/
      case '5':return OP_EIMPL;
      /*303 See Other: "The new URI is not a substitute reference for the
         originally requested resource."
        304 Not Modified: "The 304 response MUST NOT contain a message-body."
        306 (Unused)
        308...309 are not yet defined, so we don't know how to handle them.*/
      default:return OP_FALSE;
    }
    _url=NULL;
    for(;;){
      char *header;
      char *cdr;
      ret=op_http_get_next_header(&header,&cdr,&next);
      if(OP_UNLIKELY(ret<0))return ret;
      if(header==NULL)break;
      if(strcmp(header,"location")==0&&OP_LIKELY(_url==NULL))_url=cdr;
    }
    if(OP_UNLIKELY(_url==NULL))return OP_FALSE;
    /*Don't free last_host if it came from the last URL.*/
    if(last_host!=_proxy_host)_stream->url.host=NULL;
    op_parsed_url_clear(&_stream->url);
    ret=op_parse_url(&_stream->url,_url);
    if(OP_UNLIKELY(ret<0)){
      if(ret==OP_EINVAL)ret=OP_FALSE;
      if(last_host!=_proxy_host)_ogg_free((void *)last_host);
      return ret;
    }
1410
    op_http_conn_close(_stream,_stream->conns+0);
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  }
  /*Redirection limit reached.*/
  return OP_FALSE;
}

static int op_http_conn_open_pos(OpusHTTPStream *_stream,
 OpusHTTPConn *_conn,opus_int64 _pos){
  char        response[OP_RESPONSE_SIZE_MAX];
  char       *next;
  char       *status_code;
  opus_int64  range_length;
  int         ret;
  ret=op_http_connect(_stream,_conn,&_stream->addr_info);
  if(OP_UNLIKELY(ret<0))return ret;
  /*Build the request to send.*/
  _stream->request.nbuf=_stream->request_tail;
  ret=op_sb_append_nonnegative_int64(&_stream->request,_pos);
  ret|=op_sb_append(&_stream->request,"-\r\n\r\n",5);
  if(OP_UNLIKELY(ret<0))return ret;
  ret=op_http_conn_write_fully(_conn,
   _stream->request.buf,_stream->request.nbuf);
  if(OP_UNLIKELY(ret<0))return ret;
  ret=op_http_conn_read_response(_conn,
   response,sizeof(response)/sizeof(*response));
  if(OP_UNLIKELY(ret<0))return ret;
  next=op_http_parse_status_line(&status_code,response);
  if(next==NULL)return OP_FALSE;
  /*We _need_ a 206 Partial Content response.*/
  if(strncmp(status_code,"206",3)!=0)return OP_FALSE;
  range_length=-1;
  for(;;){
    char *header;
    char *cdr;
    ret=op_http_get_next_header(&header,&cdr,&next);
    if(OP_UNLIKELY(ret<0))return ret;
    if(header==NULL)break;
    if(strcmp(header,"content-range")==0){
      opus_int64 range_first;
      opus_int64 range_last;
      /*Two Content-Range headers?*/
      if(OP_UNLIKELY(range_length!=-1))return OP_FALSE;
      ret=op_http_parse_content_range(&range_first,&range_last,
       &range_length,cdr);
      if(OP_UNLIKELY(ret<0))return ret;
      /*"A response with satus code 206 (Partial Content) MUST NOTE
         include a Content-Range field with a byte-range-resp-spec of
         '*'."*/
      if(OP_UNLIKELY(range_first<0)||OP_UNLIKELY(range_last<0))return OP_FALSE;
      /*Quit if we didn't get the offset we asked for.*/
      if(range_first!=_pos)return OP_FALSE;
      /*We asked for the rest of the resource.*/
      if(range_length>=0){
        /*Quit if we didn't get it.*/
        if(OP_UNLIKELY(range_last!=range_length-1))return OP_FALSE;
      }
      /*If there was no length, use the end of the range.*/
      else if(range_last>=0)range_length=range_last+1;
    }
  }
  /*No Content-Range header.*/
  if(OP_UNLIKELY(range_length==-1))return OP_FALSE;
  /*Update the content_length if necessary.*/
  _stream->content_length=range_length;
  _conn->pos=_pos;
  _stream->cur_conni=_conn-_stream->conns;
  OP_ASSERT(_stream->cur_conni>=0&&_stream->cur_conni<OP_NCONNS_MAX);
  /*The connection has been successfully opened.*/
  return 0;
}

static size_t op_http_stream_read(void *_ptr,size_t _size,size_t _nmemb,
 void *_stream){
  OpusHTTPStream *stream;
  ptrdiff_t       nread;
  ptrdiff_t       total;
  opus_int64      size;
  opus_int64      pos;
  int             ci;
  stream=(OpusHTTPStream *)_stream;
  total=_size*_nmemb;
  /*Check for overflow/empty read.*/
  if(total==0||total/_size!=_nmemb||total>OP_INT64_MAX)return 0;
  ci=stream->cur_conni;
  /*No current connection => EOF.*/
  if(ci<0)return 0;
  pos=stream->conns[ci].pos;
  size=stream->content_length;
  /*Check for EOF.*/
  if(size!=-1){
    if(pos>=size)return 0;
    /*Check for a short read.*/
    if(total>size-pos){
      _nmemb=(size-pos)/_size;
      total=_size*_nmemb;
    }
  }
  if(_size!=1){
    ptrdiff_t n;
    nread=0;
    /*Read individual items one at a time.*/
    do{
      ptrdiff_t nread_item;
      nread_item=0;
      do{
        /*Block on the first item, or if we've gotten a partial item.*/
        n=op_http_conn_read(stream->conns+ci,
         _ptr,_size-nread_item,nread==0||nread_item>0);
        pos+=n;
        nread_item+=n;
      }
      while(n>0&&nread_item<(ptrdiff_t)_size);
      /*We can still fail to read a whole item if we encounter an error, or if
         we hit EOF and didn't know the stream length.
        TODO: The former is okay, the latter is not.*/
      if(nread_item>=(ptrdiff_t)_size)nread++;
      total-=_size;
    }
    while(n>0&&total>0);
  }
  else{
    nread=op_http_conn_read(stream->conns+ci,_ptr,total,1);
    pos+=nread;
  }
  if(OP_LIKELY(nread>0))stream->conns[ci].pos=pos;
  else{
    /*We either hit an error or EOF.
      Either way, we're done with this connection.*/
    op_http_conn_close(stream,stream->conns+ci);
    stream->cur_conni=-1;
    stream->pos=pos;
  }
  return nread;
}

/*To this will need to be larger than OP_CHUNK_SIZE to be useful.*/
# define OP_READAHEAD_THRESH (128*1024)
/*16 kB is the largest size OpenSSL will return at once.*/
# define OP_READAHEAD_CHUNK_SIZE (16*1024)

static int op_http_stream_seek(void *_stream,opus_int64 _offset,int _whence){
  OpusHTTPStream  *stream;
  OpusHTTPConn    *conn;
  OpusHTTPConn    *prev;
  OpusHTTPConn   **pnext;
  OpusHTTPConn   **ppnext;
  opus_int64       content_length;
  opus_int64       pos;
  int              ci;
  int              ret;
  stream=(OpusHTTPStream *)_stream;
  if(!stream->seekable)return -1;
  /*If we're seekable, we should have gotten a Content-Length.*/
  content_length=stream->content_length;
  OP_ASSERT(content_length>=0);
  ci=stream->cur_conni;
  pos=ci<0?content_length:stream->conns[ci].pos;
  switch(_whence){
    case SEEK_SET:{
      /*Check for overflow:*/
      if(_offset<0)return -1;
      pos=_offset;
    }break;
    case SEEK_CUR:{
      /*Check for overflow:*/
      if(_offset<-pos||_offset>OP_INT64_MAX-pos)return -1;
      pos+=_offset;
    }break;
    case SEEK_END:{
      /*Check for overflow:*/
      if(_offset>content_length||_offset<content_length-OP_INT64_MAX)return -1;
      pos=content_length-_offset;
    }break;
    default:return -1;
  }
  /*If we seeked past the end of the stream, just disable the active
     connection.*/
  if(pos>=content_length){
    stream->cur_conni=-1;
    stream->pos=pos;
    return 0;
  }
  ppnext=NULL;
  pnext=&stream->lru_head;
  prev=NULL;
  conn=stream->lru_head;
  while(conn!=NULL){
    opus_int64 conn_pos;
    /*TODO: Estimate connection open time and current throughput, and compute
       the read-ahead threshold accordingly.*/
    /*TODO: Expire connections aggressively to avoid server timeouts.*/
    conn_pos=conn->pos;
    if(pos-OP_READAHEAD_THRESH<=conn_pos&&conn_pos<=pos){
      /*Found a suitable connection to re-use.*/
      *pnext=conn->next;
      conn->next=stream->lru_head;
      stream->lru_head=conn;
      while(conn_pos<pos){
        static char dummy_buf[OP_READAHEAD_CHUNK_SIZE];
        ptrdiff_t nread;
        nread=op_http_conn_read(conn,dummy_buf,
         OP_MIN(pos-conn_pos,OP_READAHEAD_CHUNK_SIZE),1);
        if(nread==0)break;
        conn_pos+=nread;
      }
      conn->pos=conn_pos;
      /*We failed to read ahead.*/
      if(conn_pos<pos){
        op_http_conn_close(stream,conn);
        /*The connection might have become stale, so keep going.*/
        conn=*pnext;
        continue;
      }
      /*Sucessfully resurrected this connection.*/
      stream->cur_conni=conn-stream->conns;
      return 0;
    }
    ppnext=pnext;
    pnext=&conn->next;
    prev=conn;
    conn=conn->next;
  }
  /*No suitable connections.
    Open a new one.*/
  if(stream->free_head==NULL){
    /*All connections in use.
      Expire the oldest one.*/
    OP_ASSERT(prev!=NULL);
    OP_ASSERT(ppnext!=NULL);
    OP_ASSERT(prev->next==NULL);
    *ppnext=NULL;
    prev->next=stream->lru_head;
    stream->lru_head=prev;
    op_http_conn_close(stream,prev);
  }
  OP_ASSERT(stream->free_head!=NULL);
  conn=stream->free_head;
  stream->free_head=conn->next;
  conn->next=stream->lru_head;
  stream->lru_head=conn;
  ret=op_http_conn_open_pos(stream,conn,pos);
  if(OP_UNLIKELY(ret<0)){
    op_http_conn_close(stream,conn);
    return -1;
  }
  return 0;
}

static opus_int64 op_http_stream_tell(void *_stream){
  OpusHTTPStream *stream;
  int             ci;
  stream=(OpusHTTPStream *)_stream;
  ci=stream->cur_conni;
  return ci<0?stream->pos:stream->conns[ci].pos;
}

static int op_http_stream_close(void *_stream){
  OpusHTTPStream *stream;
  stream=(OpusHTTPStream *)_stream;
  if(OP_LIKELY(stream!=NULL)){
    op_http_stream_clear(stream);
    _ogg_free(stream);
  }
  return 0;
}

static const OpusFileCallbacks OP_HTTP_CALLBACKS={
  op_http_stream_read,
  op_http_stream_seek,
  op_http_stream_tell,
  op_http_stream_close
};
#endif

void *op_url_stream_create_with_proxy(OpusFileCallbacks *_cb,const char *_url,
 int _flags,const char *_proxy_host,unsigned _proxy_port,
 const char *_proxy_user,const char *_proxy_pass){
  const char *path;
  /*Check to see if this is a valid file: URL.*/
  path=op_parse_file_url(_url);
  if(path!=NULL){
    char *unescaped_path;
    void *ret;
    unescaped_path=op_string_dup(path);
    if(unescaped_path==NULL)return NULL;
    ret=op_fopen(_cb,op_unescape_url_component(unescaped_path),"rb");
    _ogg_free(unescaped_path);
    return ret;
  }
#if defined(OP_ENABLE_HTTP)
  /*If not, try http/https.*/
  else{
    OpusHTTPStream *stream;
    int             ret;
    stream=(OpusHTTPStream *)_ogg_malloc(sizeof(*stream));
    if(stream==NULL)return NULL;
    op_http_stream_init(stream);
    ret=op_http_stream_open(stream,_url,_flags,
     _proxy_host,_proxy_port,_proxy_user,_proxy_pass);
    if(OP_UNLIKELY(ret<0)){
      op_http_stream_clear(stream);
      _ogg_free(stream);
      return NULL;
    }
    *_cb=*&OP_HTTP_CALLBACKS;
    return stream;
  }
#else
  _flags=_flags;
  _proxy_host=_proxy_host;
  _proxy_port=_proxy_port;
  _proxy_user=_proxy_user;
  _proxy_pass=_proxy_pass;
  return NULL;
#endif
}

void *op_url_stream_create(OpusFileCallbacks *_cb,const char *_url,int _flags){
  return op_url_stream_create_with_proxy(_cb,_url,_flags,NULL,0,NULL,NULL);
}