Add plugin helper functions for tagfile handling

src/libvgmstream.vcproj

@@ -147,10 +147,14 @@
 			Filter="h;hpp;hxx;hm;inl;inc;xsd"
 			UniqueIdentifier="{93995380-89BD-4b04-88EB-625FBE52EBFB}"
 			>
-			<File
-				RelativePath=".\streamfile.h"
-				>
-			</File>
+            <File
+                RelativePath=".\plugins.h"
+                >
+            </File>
+            <File
+                RelativePath=".\streamfile.h"
+                >
+            </File>
 			<File
 				RelativePath=".\streamtypes.h"
 				>
@@ -172,6 +176,10 @@
             <File
                 RelativePath=".\formats.c"
                 >
+            </File>
+            <File
+                RelativePath=".\plugins.c"
+                >
             </File>
 			<File
 				RelativePath=".\streamfile.c"

src/libvgmstream.vcxproj

@@ -89,6 +89,7 @@
     <ClInclude Include="coding\vorbis_custom_data_fsb.h" />
     <ClInclude Include="coding\vorbis_custom_data_wwise.h" />
     <ClInclude Include="coding\vorbis_custom_decoder.h" />
+    <ClInclude Include="plugins.h" />
     <ClInclude Include="streamfile.h" />
     <ClInclude Include="streamtypes.h" />
     <ClInclude Include="util.h" />
@@ -189,6 +190,7 @@
     <ClCompile Include="meta\x360_cxs.c" />
     <ClCompile Include="meta\x360_tra.c" />
     <ClCompile Include="formats.c" />
+    <ClCompile Include="plugins.c" />
     <ClCompile Include="meta\ps2_va3.c" />
     <ClCompile Include="streamfile.c" />
     <ClCompile Include="util.c" />

src/libvgmstream.vcxproj.filters

@@ -47,6 +47,9 @@
     </Filter>
   </ItemGroup>
   <ItemGroup>
+    <ClInclude Include="plugins.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
     <ClInclude Include="streamfile.h">
       <Filter>Header Files</Filter>
     </ClInclude>
@@ -160,6 +163,9 @@
     <ClCompile Include="formats.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="plugins.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
     <ClCompile Include="streamfile.c">
       <Filter>Source Files</Filter>
     </ClCompile>

src/plugins.c

@@ -0,0 +1,129 @@
+#include "vgmstream.h"
+#include "plugins.h"
+
+
+static void tags_clean(VGMSTREAM_TAGS* tag) {
+    int i;
+    int val_len = strlen(tag->val);
+
+    /* remove trailing spaces */
+    for (i = val_len - 1; i > 0; i--) {
+        if (tag->val[i] != ' ')
+            break;
+        tag->val[i] = '\0';
+    }
+}
+
+/* Tags are divided in two: "global" @TAGS and "file" %TAGS for target filename. To extract both
+ * we find the filename's tag "section": (other_filename) ..(#tag section).. (target_filename).
+ * When a new "other_filename" is found that offset is marked as section_start, and when target_filename
+ * is found it's marked as section_end. Then we can begin extracting tags within that section, until
+ * all tags are exhausted. Global tags are extracted while searching, so they always go first, and
+ * also meaning any tags after the section is found are ignored. */
+int vgmstream_tags_next_tag(VGMSTREAM_TAGS* tag, STREAMFILE* tagfile) {
+    off_t file_size = get_streamfile_size(tagfile);
+    char currentname[TAG_LINE_MAX] = {0};
+    char line[TAG_LINE_MAX] = {0};
+    int ok, bytes_read, line_done;
+
+
+    /* prepare file start and skip BOM if needed */
+    if (tag->offset == 0) {
+        if ((uint16_t)read_16bitLE(0x00, tagfile) == 0xFFFE ||
+            (uint16_t)read_16bitLE(0x00, tagfile) == 0xFEFF) {
+            tag->offset = 0x02;
+            if (tag->section_start == 0)
+                tag->section_start = 0x02;
+        }
+        else if (((uint32_t)read_32bitBE(0x00, tagfile) & 0xFFFFFF00) ==  0xEFBBBF00) {
+            tag->offset = 0x03;
+            if (tag->section_start == 0)
+                tag->section_start = 0x03;
+        }
+    }
+
+    /* read lines */
+    while (tag->offset < file_size) {
+        /* no more tags to extract */
+        if (tag->section_found && tag->offset >= tag->section_end) {
+            goto fail;
+        }
+
+        bytes_read = get_streamfile_text_line(TAG_LINE_MAX,line, tag->offset,tagfile, &line_done);
+        if (!line_done) goto fail;
+
+        tag->offset += bytes_read;
+
+
+        if (tag->section_found) {
+            /* find possible file tag */
+            ok = sscanf(line, "# %%%[^ \t] %[^\r\n] ", tag->key,tag->val);
+            if (ok == 2) {
+                tags_clean(tag);
+                return 1;
+            }
+        }
+        else {
+            /* find possible global tag */
+            if (line[0] == '#') {
+                ok = sscanf(line, "# @%[^ \t] %[^\r\n]", tag->key,tag->val);
+                if (ok == 2) {
+                    tags_clean(tag);
+                    return 1;
+                }
+
+                continue; /* next line */
+            }
+
+            /* find possible filename and section start/end */
+            ok = sscanf(line, " %[^\r\n] ", currentname);
+            if (ok == 1)  {
+                if (strcasecmp(tag->targetname,currentname) == 0) { /* looks ok even for UTF-8 */
+                    /* section ok, start would be set before this (or be 0) */
+                    tag->section_end = tag->offset;
+                    tag->section_found = 1;
+                    tag->offset = tag->section_start;
+                }
+                else {
+                    /* mark new possible section */
+                    tag->section_start = tag->offset;
+                }
+
+                continue;
+            }
+
+            /* empty/bad line, probably */
+        }
+    }
+
+    /* may reach here if read up to file_size but no section was found */
+
+fail:
+    tag->key[0] = '\0';
+    tag->val[0] = '\0';
+    return 0;
+}
+
+
+void vgmstream_tags_reset(VGMSTREAM_TAGS* tag, const char* target_filename) {
+    const char *path;
+
+    memset(tag, 0, sizeof(VGMSTREAM_TAGS));
+
+
+    /* get base name */
+
+    //todo Windows CMD accepts both \\ and /, better way to handle this?
+    path = strrchr(target_filename,'\\');
+    if (!path)
+        path = strrchr(target_filename,'/');
+    if (path != NULL)
+        path = path+1;
+
+    //todo validate sizes and copy sensible max
+    if (path) {
+        strcpy(tag->targetname, path);
+    } else {
+        strcpy(tag->targetname, target_filename);
+    }
+}

src/plugins.h

@@ -0,0 +1,36 @@
+/*
+ * plugins.h - helper for plugins
+ */
+#ifndef _PLUGINS_H_
+#define _PLUGINS_H_
+
+#include "streamfile.h"
+#define TAG_LINE_MAX 2048
+
+//todo improve API and make opaque
+//typedef struct VGMSTREAM_TAGS VGMSTREAM_TAGS;
+typedef struct {
+    /* extracted output */
+    char key[TAG_LINE_MAX];
+    char val[TAG_LINE_MAX];
+
+    /* file to find tags for */
+    char targetname[TAG_LINE_MAX];
+
+    /* tag section for filename (see comments below) */
+    int section_found;
+    off_t section_start;
+    off_t section_end;
+    off_t offset;
+} VGMSTREAM_TAGS;
+
+
+
+/* Extracts next valid tag in tagfile to *tag. Returns 0 if no more tags are found (meant to be
+ * called repeatedly until 0). Key are lowercase and values can be treated as UTF-8. */
+int vgmstream_tags_next_tag(VGMSTREAM_TAGS* tag, STREAMFILE* tagfile);
+
+/* resets tagfile to restart reading from the beginning for a new filename */
+void vgmstream_tags_reset(VGMSTREAM_TAGS* tag, const char* target_filename);
+
+#endif /* _PLUGINS_H_ */