consolidate chain error reporting in a single function, add extra explanation for common errors

src/metaflac/operations.c

@@ -109,7 +109,7 @@ FLAC__bool do_major_operation_on_file(const char *filename, const CommandLineOpt
 		die("out of memory allocating chain");
 
 	if(!FLAC__metadata_chain_read(chain, filename)) {
-		fprintf(stderr, "%s: ERROR: reading metadata, status = \"%s\"\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+		print_error_with_chain_status(chain, "%s: ERROR: reading metadata", filename);
 		return false;
 	}
 
@@ -147,7 +147,7 @@ FLAC__bool do_major_operation_on_file(const char *filename, const CommandLineOpt
 			FLAC__metadata_chain_sort_padding(chain);
 		ok = FLAC__metadata_chain_write(chain, options->use_padding, options->preserve_modtime);
 		if(!ok)
-			fprintf(stderr, "%s: ERROR: writing FLAC file, error = %s\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+			print_error_with_chain_status(chain, "%s: ERROR: writing FLAC file", filename);
 	}
 
 	FLAC__metadata_chain_delete(chain);
@@ -267,7 +267,7 @@ FLAC__bool do_shorthand_operations_on_file(const char *filename, const CommandLi
 		die("out of memory allocating chain");
 
 	if(!FLAC__metadata_chain_read(chain, filename)) {
-		fprintf(stderr, "%s: ERROR: reading metadata, status = \"%s\"\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+		print_error_with_chain_status(chain, "%s: ERROR: reading metadata", filename);
 		return false;
 	}
 
@@ -304,7 +304,7 @@ FLAC__bool do_shorthand_operations_on_file(const char *filename, const CommandLi
 			FLAC__metadata_chain_sort_padding(chain);
 		ok = FLAC__metadata_chain_write(chain, use_padding, options->preserve_modtime);
 		if(!ok)
-			fprintf(stderr, "%s: ERROR: writing FLAC file, error = %s\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+			print_error_with_chain_status(chain, "%s: ERROR: writing FLAC file", filename);
 	}
 
 	FLAC__metadata_chain_delete(chain);
@@ -478,7 +478,7 @@ FLAC__bool do_shorthand_operation__add_padding(const char *filename, FLAC__Metad
 	padding->length = length;
 
 	if(!FLAC__metadata_iterator_insert_block_after(iterator, padding)) {
-		fprintf(stderr, "%s: ERROR: adding new PADDING block to metadata, status =\"%s\"\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+		print_error_with_chain_status(chain, "%s: ERROR: adding new PADDING block to metadata", filename);
 		FLAC__metadata_object_delete(padding);
 		FLAC__metadata_iterator_delete(iterator);
 		return false;

src/metaflac/operations_shorthand_cuesheet.c

@@ -75,7 +75,7 @@ FLAC__bool do_shorthand_operation__cuesheet(const char *filename, FLAC__Metadata
 					while(FLAC__metadata_iterator_next(iterator))
 						;
 					if(!FLAC__metadata_iterator_insert_block_after(iterator, cuesheet)) {
-						fprintf(stderr, "%s: ERROR: adding new CUESHEET block to metadata, status =\"%s\"\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+						print_error_with_chain_status(chain, "%s: ERROR: adding new CUESHEET block to metadata", filename);
 						FLAC__metadata_object_delete(cuesheet);
 						ok = false;
 					}

src/metaflac/operations_shorthand_seektable.c

@@ -60,7 +60,7 @@ FLAC__bool do_shorthand_operation__add_seekpoints(const char *filename, FLAC__Me
 		while(FLAC__metadata_iterator_prev(iterator))
 			;
 		if(!FLAC__metadata_iterator_insert_block_after(iterator, block)) {
-			fprintf(stderr, "%s: ERROR: adding new SEEKTABLE block to metadata, status =\"%s\"\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+			print_error_with_chain_status(chain, "%s: ERROR: adding new SEEKTABLE block to metadata", filename);
 			FLAC__metadata_object_delete(block);
 			return false;
 		}

src/metaflac/operations_shorthand_vorbiscomment.c

@@ -56,7 +56,7 @@ FLAC__bool do_shorthand_operation__vorbis_comment(const char *filename, FLAC__bo
 			while(FLAC__metadata_iterator_next(iterator))
 				;
 			if(!FLAC__metadata_iterator_insert_block_after(iterator, block)) {
-				fprintf(stderr, "%s: ERROR: adding new VORBIS_COMMENT block to metadata, status =\"%s\"\n", filename, FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)]);
+				print_error_with_chain_status(chain, "%s: ERROR: adding new VORBIS_COMMENT block to metadata", filename);
 				return false;
 			}
 			/* iterator is left pointing to new block */

src/metaflac/utils.c

@@ -20,6 +20,7 @@
 #include "FLAC/assert.h"
 #include "share/utf8.h"
 #include <ctype.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -119,6 +120,61 @@ void hexdump(const char *filename, const FLAC__byte *buf, unsigned bytes, const
    }
 }
 
+void print_error_with_chain_status(FLAC__Metadata_Chain *chain, const char *format, ...)
+{
+	const FLAC__Metadata_ChainStatus status = FLAC__metadata_chain_status(chain);
+	va_list args;
+
+	FLAC__ASSERT(0 != format);
+
+	va_start(args, format);
+
+	(void) vfprintf(stderr, format, args);
+
+	va_end(args);
+
+	fprintf(stderr, ", status = \"%s\"\n", FLAC__Metadata_ChainStatusString[status]);
+
+	if(status == FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE) {
+		fprintf(stderr, "\n"
+			"The FLAC file could not be opened.  Most likely the file does not exist\n"
+			"or is not readable.\n"
+		);
+	}
+	else if(status == FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE) {
+		fprintf(stderr, "\n"
+			"The file does not appear to be a FLAC file.\n"
+		);
+	}
+	else if(status == FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE) {
+		fprintf(stderr, "\n"
+			"The FLAC file does not have write permissions.\n"
+		);
+	}
+	else if(status == FLAC__METADATA_CHAIN_STATUS_BAD_METADATA) {
+		fprintf(stderr, "\n"
+			"The metadata to be writted does not conform to the FLAC metadata\n"
+			"specifications.\n"
+		);
+	}
+	else if(status == FLAC__METADATA_CHAIN_STATUS_READ_ERROR) {
+		fprintf(stderr, "\n"
+			"There was an error while reading the FLAC file.\n"
+		);
+	}
+	else if(status == FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR) {
+		fprintf(stderr, "\n"
+			"There was an error while writing FLAC file; most probably the disk is\n"
+			"full.\n"
+		);
+	}
+	else if(status == FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR) {
+		fprintf(stderr, "\n"
+			"There was an error removing the temporary FLAC file.\n"
+		);
+	}
+}
+
 FLAC__bool parse_vorbis_comment_field(const char *field_ref, char **field, char **name, char **value, unsigned *length, const char **violation)
 {
 	static const char * const violations[] = {

src/metaflac/utils.h

@@ -31,6 +31,7 @@ size_t local_fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream);
 char *local_strdup(const char *source);
 void local_strcat(char **dest, const char *source);
 void hexdump(const char *filename, const FLAC__byte *buf, unsigned bytes, const char *indent);
+void print_error_with_chain_status(FLAC__Metadata_Chain *chain, const char *format, ...);
 
 FLAC__bool parse_vorbis_comment_field(const char *field_ref, char **field, char **name, char **value, unsigned *length, const char **violation);