shithub: opusfile

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Expose tag comparison functions.

It seems somewhat silly to have to write your own strcasecmp to
 satisfy the usage pattern found in opusfile_example: scanning the
 whole tags list and handling certain tags specially (as opposed to
 searching for specific tags, as opus_tags_query() does).
Given that we were already using an equivalent function internally
 to implement opus_tags_query, just expose it directly.

--- a/examples/opusfile_example.c

+++ b/examples/opusfile_example.c

@@ -93,24 +93,6 @@

   else fprintf(_fp,"%li%s%c",(long)val,_spacer,SUFFIXES[shift]);

 }

-/*A version of strncasecmp() that is guaranteed to only ignore the case of

-   ASCII characters.*/

-static int local_strncasecmp(const char *_a,const char *_b,int _n){

-  int i;

-  for(i=0;i<_n;i++){

-    int a;

-    int b;

-    int d;

-    a=_a[i];

-    b=_b[i];

-    if(a>='a'&&a<='z')a-='a'-'A';

-    if(b>='a'&&b<='z')b-='a'-'A';

-    d=a-b;

-    if(d)return d;

-  }

-  return 0;

-}

-

 static void put_le32(unsigned char *_dst,opus_uint32 _x){

   _dst[0]=(unsigned char)(_x&0xFF);

   _dst[1]=(unsigned char)(_x>>8&0xFF);

@@ -304,7 +286,7 @@

         for(ci=0;ci<tags->comments;ci++){

           const char *comment;

           comment=tags->user_comments[ci];

-          if(local_strncasecmp(comment,"METADATA_BLOCK_PICTURE=",23)==0){

+          if(opus_tagncompare("METADATA_BLOCK_PICTURE",22,comment)==0){

             OpusPictureTag pic;

             int            err;

             err=opus_picture_tag_parse(&pic,comment);

--- a/include/opusfile.h

+++ b/include/opusfile.h

@@ -547,6 +547,32 @@

    \param _tags The #OpusTags structure to clear.*/

 void opus_tags_clear(OpusTags *_tags) OP_ARG_NONNULL(1);

+/**Check if \a _comment is an instance of a \a _tag_name tag.

+   \see opus_tagncompare

+   \param _tag_name A NUL-terminated, case-insensitive, ASCII string containing

+                     the name of the tag to check for (without the terminating

+                     '=' character).

+   \param _comment  The comment string to check.

+   \return An integer less than, equal to, or greater than zero if \a _comment

+            is found respectively, to be less than, to match, or be greater

+            than a "tag=value" string whose tag matches \a _tag_name.*/

+int opus_tagcompare(const char *_tag_name,const char *_comment);

+

+/**Check if \a _comment is an instance of a \a _tag_name tag.

+   This version is slightly more efficient than opus_tagcompare() if the length

+    of the tag name is already known (e.g., because it is a constant).

+   \see opus_tagcompare

+   \param _tag_name A case-insensitive ASCII string containing the name of the

+                     tag to check for (without the terminating '=' character).

+   \param _tag_len  The number of characters in the tag name.

+                    This must be non-negative.

+   \param _comment  The comment string to check.

+   \return An integer less than, equal to, or greater than zero if \a _comment

+            is found respectively, to be less than, to match, or be greater

+            than a "tag=value" string whose tag matches the first \a _tag_len

+            characters of \a _tag_name.*/

+int opus_tagncompare(const char *_tag_name,int _tag_len,const char *_comment);

+

 /**Parse a single METADATA_BLOCK_PICTURE tag.

    This decodes the BASE64-encoded content of the tag and returns a structure

     with the MIME type, description, image parameters (if known), and the

--- a/src/info.c

+++ b/src/info.c

@@ -251,12 +251,17 @@

   return 0;

 }

-/*Is _a a "tag=value" comment whose tag matches _b?

-  0 if it is, a non-zero value otherwise.*/

-static int op_tagcompare(const char *_a,const char *_b,int _n){

-  return op_strncasecmp(_a,_b,_n)||_a[_n]!='=';

+int opus_tagcompare(const char *_tag_name,const char *_comment){

+  return opus_tagncompare(_tag_name,strlen(_tag_name),_comment);

 }

+int opus_tagncompare(const char *_tag_name,int _tag_len,const char *_comment){

+  int ret;

+  OP_ASSERT(_tag_len>=0);

+  ret=op_strncasecmp(_tag_name,_comment,_tag_len);

+  return ret?ret:'='-_comment[_tag_len];

+}

+

 const char *opus_tags_query(const OpusTags *_tags,const char *_tag,int _count){

   char **user_comments;

   int    tag_len;

@@ -268,7 +273,7 @@

   user_comments=_tags->user_comments;

   found=0;

   for(ci=0;ci<ncomments;ci++){

-    if(!op_tagcompare(user_comments[ci],_tag,tag_len)){

+    if(!opus_tagncompare(_tag,tag_len,user_comments[ci])){

       /*We return a pointer to the data, not a copy.*/

       if(_count==found++)return user_comments[ci]+tag_len+1;

     }

@@ -288,7 +293,7 @@

   user_comments=_tags->user_comments;

   found=0;

   for(ci=0;ci<ncomments;ci++){

-    if(!op_tagcompare(user_comments[ci],_tag,tag_len))found++;

+    if(!opus_tagncompare(_tag,tag_len,user_comments[ci]))found++;

   }

   return found;

 }