[FFmpeg-devel] [Read EXIF metadata 1/3] Refactor TIFF tag related functions to share the code.

Thilo Borgmann thilo.borgmann at googlemail.com
Fri Aug 2 22:15:05 CEST 2013


Updated Patch according to latest comments.

-Thilo
-------------- next part --------------
>From d64662e9507a62fd3eef7d46c9dee1b0ea07b9cd Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann at googlemail.com>
Date: Fri, 2 Aug 2013 22:10:05 +0200
Subject: [PATCH] Refactor TIFF tag related functions to share the code.

---
 libavcodec/Makefile      |    2 +-
 libavcodec/tiff.c        |  235 +++++----------------------------------------
 libavcodec/tiff.h        |   22 +----
 libavcodec/tiff_common.c |  240 ++++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/tiff_common.h |  113 ++++++++++++++++++++++
 5 files changed, 380 insertions(+), 232 deletions(-)
 create mode 100644 libavcodec/tiff_common.c
 create mode 100644 libavcodec/tiff_common.h

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 31477ac..5e2e894 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -421,7 +421,7 @@ OBJS-$(CONFIG_TARGA_Y216_DECODER)      += targa_y216dec.o
 OBJS-$(CONFIG_THEORA_DECODER)          += xiph.o
 OBJS-$(CONFIG_THP_DECODER)             += mjpegdec.o mjpeg.o
 OBJS-$(CONFIG_TIERTEXSEQVIDEO_DECODER) += tiertexseqv.o
-OBJS-$(CONFIG_TIFF_DECODER)            += tiff.o lzw.o faxcompr.o tiff_data.o
+OBJS-$(CONFIG_TIFF_DECODER)            += tiff.o lzw.o faxcompr.o tiff_data.o tiff_common.o
 OBJS-$(CONFIG_TIFF_ENCODER)            += tiffenc.o rle.o lzwenc.o tiff_data.o
 OBJS-$(CONFIG_TMV_DECODER)             += tmv.o cga_data.o
 OBJS-$(CONFIG_TRUEHD_DECODER)          += mlpdec.o mlpdsp.o
diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
index fdfa8f2..fe56754 100644
--- a/libavcodec/tiff.c
+++ b/libavcodec/tiff.c
@@ -70,38 +70,6 @@ typedef struct TiffContext {
     TiffGeoTag *geotags;
 } TiffContext;
 
-static unsigned tget_short(GetByteContext *gb, int le)
-{
-    unsigned v = le ? bytestream2_get_le16(gb) : bytestream2_get_be16(gb);
-    return v;
-}
-
-static unsigned tget_long(GetByteContext *gb, int le)
-{
-    unsigned v = le ? bytestream2_get_le32(gb) : bytestream2_get_be32(gb);
-    return v;
-}
-
-static double tget_double(GetByteContext *gb, int le)
-{
-    av_alias64 i = { .u64 = le ? bytestream2_get_le64(gb) : bytestream2_get_be64(gb)};
-    return i.f64;
-}
-
-static unsigned tget(GetByteContext *gb, int type, int le)
-{
-    switch (type) {
-    case TIFF_BYTE:
-        return bytestream2_get_byte(gb);
-    case TIFF_SHORT:
-        return tget_short(gb, le);
-    case TIFF_LONG:
-        return tget_long(gb, le);
-    default:
-        return UINT_MAX;
-    }
-}
-
 static void free_geotags(TiffContext *const s)
 {
     int i;
@@ -219,137 +187,13 @@ static char *get_geokey_val(int key, int val)
     return ap;
 }
 
-static char *doubles2str(double *dp, int count, const char *sep)
-{
-    int i;
-    char *ap, *ap0;
-    uint64_t component_len;
-    if (!sep) sep = ", ";
-    component_len = 15LL + strlen(sep);
-    if (count >= (INT_MAX - 1)/component_len)
-        return NULL;
-    ap = av_malloc(component_len * count + 1);
-    if (!ap)
-        return NULL;
-    ap0   = ap;
-    ap[0] = '\0';
-    for (i = 0; i < count; i++) {
-        unsigned l = snprintf(ap, component_len, "%f%s", dp[i], sep);
-        if(l >= component_len) {
-            av_free(ap0);
-            return NULL;
-        }
-        ap += l;
-    }
-    ap0[strlen(ap0) - strlen(sep)] = '\0';
-    return ap0;
-}
-
-static char *shorts2str(int16_t *sp, int count, const char *sep)
-{
-    int i;
-    char *ap, *ap0;
-    uint64_t component_len;
-    if (!sep) sep = ", ";
-    component_len = 7LL + strlen(sep);
-    if (count >= (INT_MAX - 1)/component_len)
-        return NULL;
-    ap = av_malloc(component_len * count + 1);
-    if (!ap)
-        return NULL;
-    ap0   = ap;
-    ap[0] = '\0';
-    for (i = 0; i < count; i++) {
-        unsigned l = snprintf(ap, component_len, "%d%s", sp[i], sep);
-        if (l >= component_len) {
-            av_free(ap0);
-            return NULL;
-        }
-        ap += l;
-    }
-    ap0[strlen(ap0) - strlen(sep)] = '\0';
-    return ap0;
-}
-
-static int add_doubles_metadata(int count,
-                                const char *name, const char *sep,
-                                TiffContext *s, AVFrame *frame)
-{
-    char *ap;
-    int i;
-    double *dp;
-
-    if (count >= INT_MAX / sizeof(int64_t) || count <= 0)
-        return AVERROR_INVALIDDATA;
-    if (bytestream2_get_bytes_left(&s->gb) < count * sizeof(int64_t))
-        return AVERROR_INVALIDDATA;
-
-    dp = av_malloc(count * sizeof(double));
-    if (!dp)
-        return AVERROR(ENOMEM);
-
-    for (i = 0; i < count; i++)
-        dp[i] = tget_double(&s->gb, s->le);
-    ap = doubles2str(dp, count, sep);
-    av_freep(&dp);
-    if (!ap)
-        return AVERROR(ENOMEM);
-    av_dict_set(avpriv_frame_get_metadatap(frame), name, ap, AV_DICT_DONT_STRDUP_VAL);
-    return 0;
-}
-
-static int add_shorts_metadata(int count, const char *name,
-                               const char *sep, TiffContext *s, AVFrame *frame)
-{
-    char *ap;
-    int i;
-    int16_t *sp;
-
-    if (count >= INT_MAX / sizeof(int16_t) || count <= 0)
-        return AVERROR_INVALIDDATA;
-    if (bytestream2_get_bytes_left(&s->gb) < count * sizeof(int16_t))
-        return AVERROR_INVALIDDATA;
-
-    sp = av_malloc(count * sizeof(int16_t));
-    if (!sp)
-        return AVERROR(ENOMEM);
-
-    for (i = 0; i < count; i++)
-        sp[i] = tget_short(&s->gb, s->le);
-    ap = shorts2str(sp, count, sep);
-    av_freep(&sp);
-    if (!ap)
-        return AVERROR(ENOMEM);
-    av_dict_set(avpriv_frame_get_metadatap(frame), name, ap, AV_DICT_DONT_STRDUP_VAL);
-    return 0;
-}
-
-static int add_string_metadata(int count, const char *name,
-                               TiffContext *s, AVFrame *frame)
-{
-    char *value;
-
-    if (bytestream2_get_bytes_left(&s->gb) < count || count < 0)
-        return AVERROR_INVALIDDATA;
-
-    value = av_malloc(count + 1);
-    if (!value)
-        return AVERROR(ENOMEM);
-
-    bytestream2_get_bufferu(&s->gb, value, count);
-    value[count] = 0;
-
-    av_dict_set(avpriv_frame_get_metadatap(frame), name, value, AV_DICT_DONT_STRDUP_VAL);
-    return 0;
-}
-
 static int add_metadata(int count, int type,
                         const char *name, const char *sep, TiffContext *s, AVFrame *frame)
 {
     switch(type) {
-    case TIFF_DOUBLE: return add_doubles_metadata(count, name, sep, s, frame);
-    case TIFF_SHORT : return add_shorts_metadata(count, name, sep, s, frame);
-    case TIFF_STRING: return add_string_metadata(count, name, s, frame);
+    case TIFF_DOUBLE: return ff_tadd_doubles_metadata(count, name, sep, &s->gb, s->le, avpriv_frame_get_metadatap(frame));
+    case TIFF_SHORT : return ff_tadd_shorts_metadata(count, name, sep, &s->gb, s->le, avpriv_frame_get_metadatap(frame));
+    case TIFF_STRING: return ff_tadd_string_metadata(count, name, &s->gb, s->le, avpriv_frame_get_metadatap(frame));
     default         : return AVERROR_INVALIDDATA;
     };
 }
@@ -702,10 +546,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
     uint32_t *pal;
     double *dp;
 
-    tag   = tget_short(&s->gb, s->le);
-    type  = tget_short(&s->gb, s->le);
-    count = tget_long(&s->gb, s->le);
-    off   = tget_long(&s->gb, s->le);
+    ff_tread_tag_data(&s->gb, s->le, &tag, &type, &count, &off);
     start = bytestream2_tell(&s->gb);
 
     if (type == 0 || type >= FF_ARRAY_ELEMS(type_sizes)) {
@@ -714,30 +555,20 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
         return 0;
     }
 
+    ff_tseek_tag_value(&s->gb, type, count, off);
     if (count == 1) {
         switch (type) {
         case TIFF_BYTE:
         case TIFF_SHORT:
-            bytestream2_seek(&s->gb, -4, SEEK_CUR);
-            value = tget(&s->gb, type, s->le);
+            value = ff_tget(&s->gb, type, s->le);
             break;
         case TIFF_LONG:
             value = off;
             break;
-        case TIFF_STRING:
-            if (count <= 4) {
-                bytestream2_seek(&s->gb, -4, SEEK_CUR);
-                break;
-            }
         default:
             value = UINT_MAX;
             bytestream2_seek(&s->gb, off, SEEK_SET);
         }
-    } else {
-        if (count <= 4 && type_sizes[type] * count <= 4)
-            bytestream2_seek(&s->gb, -4, SEEK_CUR);
-        else
-            bytestream2_seek(&s->gb, off, SEEK_SET);
     }
 
     switch (tag) {
@@ -769,7 +600,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
                 if (bytestream2_get_bytes_left(&s->gb) < type_sizes[type] * count)
                     return AVERROR_INVALIDDATA;
                 for (i = 0; i < count; i++)
-                    s->bpp += tget(&s->gb, type, s->le);
+                    s->bpp += ff_tget(&s->gb, type, s->le);
                 break;
             default:
                 s->bpp = -1;
@@ -909,7 +740,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             for (i = 0; i < count / 3; i++) {
                 if (k == 2)
                     pal[i] = 0xFFU << 24;
-                j =  (tget(&s->gb, type, s->le) >> off) << (k * 8);
+                j =  (ff_tget(&s->gb, type, s->le) >> off) << (k * 8);
                 pal[i] |= j;
             }
         }
@@ -943,7 +774,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
     case TIFF_GEO_KEY_DIRECTORY:
         ADD_METADATA(1, "GeoTIFF_Version", NULL);
         ADD_METADATA(2, "GeoTIFF_Key_Revision", ".");
-        s->geotag_count   = tget_short(&s->gb, s->le);
+        s->geotag_count   = ff_tget_short(&s->gb, s->le);
         if (s->geotag_count > count / 4 - 1) {
             s->geotag_count = count / 4 - 1;
             av_log(s->avctx, AV_LOG_WARNING, "GeoTIFF key directory buffer shorter than specified\n");
@@ -959,14 +790,14 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             return AVERROR(ENOMEM);
         }
         for (i = 0; i < s->geotag_count; i++) {
-            s->geotags[i].key    = tget_short(&s->gb, s->le);
-            s->geotags[i].type   = tget_short(&s->gb, s->le);
-            s->geotags[i].count  = tget_short(&s->gb, s->le);
+            s->geotags[i].key    = ff_tget_short(&s->gb, s->le);
+            s->geotags[i].type   = ff_tget_short(&s->gb, s->le);
+            s->geotags[i].count  = ff_tget_short(&s->gb, s->le);
 
             if (!s->geotags[i].type)
-                s->geotags[i].val  = get_geokey_val(s->geotags[i].key, tget_short(&s->gb, s->le));
+                s->geotags[i].val  = get_geokey_val(s->geotags[i].key, ff_tget_short(&s->gb, s->le));
             else
-                s->geotags[i].offset = tget_short(&s->gb, s->le);
+                s->geotags[i].offset = ff_tget_short(&s->gb, s->le);
         }
         break;
     case TIFF_GEO_DOUBLE_PARAMS:
@@ -980,14 +811,14 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             return AVERROR(ENOMEM);
         }
         for (i = 0; i < count; i++)
-            dp[i] = tget_double(&s->gb, s->le);
+            dp[i] = ff_tget_double(&s->gb, s->le);
         for (i = 0; i < s->geotag_count; i++) {
             if (s->geotags[i].type == TIFF_GEO_DOUBLE_PARAMS) {
                 if (s->geotags[i].count == 0
                     || s->geotags[i].offset + s->geotags[i].count > count) {
                     av_log(s->avctx, AV_LOG_WARNING, "Invalid GeoTIFF key %d\n", s->geotags[i].key);
                 } else {
-                    char *ap = doubles2str(&dp[s->geotags[i].offset], s->geotags[i].count, ", ");
+                    char *ap = ff_tdoubles2str(&dp[s->geotags[i].offset], s->geotags[i].count, ", ");
                     if (!ap) {
                         av_log(s->avctx, AV_LOG_ERROR, "Error allocating temporary buffer\n");
                         av_freep(&dp);
@@ -1075,7 +906,7 @@ static int decode_frame(AVCodecContext *avctx,
     TiffContext *const s = avctx->priv_data;
     AVFrame *const p = data;
     unsigned off;
-    int id, le, ret, plane, planes;
+    int le, ret, plane, planes;
     int i, j, entries, stride;
     unsigned soff, ssize;
     uint8_t *dst;
@@ -1085,15 +916,11 @@ static int decode_frame(AVCodecContext *avctx,
     bytestream2_init(&s->gb, avpkt->data, avpkt->size);
 
     // parse image header
-    if (avpkt->size < 8)
-        return AVERROR_INVALIDDATA;
-    id   = bytestream2_get_le16u(&s->gb);
-    if (id == 0x4949)
-        le = 1;
-    else if (id == 0x4D4D)
-        le = 0;
-    else {
-        av_log(avctx, AV_LOG_ERROR, "TIFF header not found\n");
+    if ((ret = ff_tdecode_header(&s->gb, &le, &off))) {
+        av_log(avctx, AV_LOG_ERROR, "Invalid TIFF header\n");
+        return ret;
+    } else if (off >= UINT_MAX - 14 || avpkt->size < off + 14) {
+        av_log(avctx, AV_LOG_ERROR, "IFD offset is greater than image size\n");
         return AVERROR_INVALIDDATA;
     }
     s->le         = le;
@@ -1104,23 +931,11 @@ static int decode_frame(AVCodecContext *avctx,
     s->fill_order = 0;
     free_geotags(s);
 
-    // As TIFF 6.0 specification puts it "An arbitrary but carefully chosen number
-    // that further identifies the file as a TIFF file"
-    if (tget_short(&s->gb, le) != 42) {
-        av_log(avctx, AV_LOG_ERROR,
-               "The answer to life, universe and everything is not correct!\n");
-        return AVERROR_INVALIDDATA;
-    }
     // Reset these offsets so we can tell if they were set this frame
     s->stripsizesoff = s->strippos = 0;
     /* parse image file directory */
-    off = tget_long(&s->gb, le);
-    if (off >= UINT_MAX - 14 || avpkt->size < off + 14) {
-        av_log(avctx, AV_LOG_ERROR, "IFD offset is greater than image size\n");
-        return AVERROR_INVALIDDATA;
-    }
     bytestream2_seek(&s->gb, off, SEEK_SET);
-    entries = tget_short(&s->gb, le);
+    entries = ff_tget_short(&s->gb, le);
     if (bytestream2_get_bytes_left(&s->gb) < entries * 12)
         return AVERROR_INVALIDDATA;
     for (i = 0; i < entries; i++) {
@@ -1180,12 +995,12 @@ static int decode_frame(AVCodecContext *avctx,
         dst    = p->data[plane];
     for (i = 0; i < s->height; i += s->rps) {
         if (s->stripsizesoff)
-            ssize = tget(&stripsizes, s->sstype, s->le);
+            ssize = ff_tget(&stripsizes, s->sstype, s->le);
         else
             ssize = s->stripsize;
 
         if (s->strippos)
-            soff = tget(&stripdata, s->sot, s->le);
+            soff = ff_tget(&stripdata, s->sot, s->le);
         else
             soff = s->stripoff;
 
diff --git a/libavcodec/tiff.h b/libavcodec/tiff.h
index 3ea2158..ae189b6 100644
--- a/libavcodec/tiff.h
+++ b/libavcodec/tiff.h
@@ -31,6 +31,7 @@
 #define AVCODEC_TIFF_H
 
 #include <stdint.h>
+#include "tiff_common.h"
 
 /** abridged list of TIFF tags */
 enum TiffTags {
@@ -97,22 +98,6 @@ enum TiffCompr {
     TIFF_DEFLATE  = 0x80B2
 };
 
-enum TiffTypes {
-    TIFF_BYTE = 1,
-    TIFF_STRING,
-    TIFF_SHORT,
-    TIFF_LONG,
-    TIFF_RATIONAL,
-    TIFF_SBYTE,
-    TIFF_UNDEFINED,
-    TIFF_SSHORT,
-    TIFF_SLONG,
-    TIFF_SRATIONAL,
-    TIFF_FLOAT,
-    TIFF_DOUBLE,
-    TIFF_IFD
-};
-
 enum TiffGeoTagKey {
     TIFF_GT_MODEL_TYPE_GEOKEY                = 1024,
     TIFF_GT_RASTER_TYPE_GEOKEY               = 1025,
@@ -167,11 +152,6 @@ enum TiffGeoTagType {
     GEOTIFF_STRING = 34737
 };
 
-/** sizes of various TIFF field types (string size = 100)*/
-static const uint8_t type_sizes[14] = {
-    0, 1, 100, 2, 4, 8, 1, 1, 2, 4, 8, 4, 8, 4
-};
-
 typedef struct TiffGeoTag {
     enum TiffGeoTagKey key;
     enum TiffTags type;
diff --git a/libavcodec/tiff_common.c b/libavcodec/tiff_common.c
new file mode 100644
index 0000000..b09810a
--- /dev/null
+++ b/libavcodec/tiff_common.c
@@ -0,0 +1,240 @@
+/*
+ * TIFF Common Routines
+ * Copyright (c) 2013 Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * TIFF Common Routines
+ * @author Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
+ */
+
+#include "tiff_common.h"
+
+
+unsigned ff_tget_short(GetByteContext *gb, int le)
+{
+    unsigned v = le ? bytestream2_get_le16(gb) : bytestream2_get_be16(gb);
+    return v;
+}
+
+
+unsigned ff_tget_long(GetByteContext *gb, int le)
+{
+    unsigned v = le ? bytestream2_get_le32(gb) : bytestream2_get_be32(gb);
+    return v;
+}
+
+
+double ff_tget_double(GetByteContext *gb, int le)
+{
+    av_alias64 i = { .u64 = le ? bytestream2_get_le64(gb) : bytestream2_get_be64(gb)};
+    return i.f64;
+}
+
+
+unsigned ff_tget(GetByteContext *gb, int type, int le)
+{
+    switch (type) {
+    case TIFF_BYTE:
+        return bytestream2_get_byte(gb);
+    case TIFF_SHORT:
+        return ff_tget_short(gb, le);
+    case TIFF_LONG:
+        return ff_tget_long(gb, le);
+    default:
+        return UINT_MAX;
+    }
+}
+
+
+char *ff_tdoubles2str(double *dp, int count, const char *sep)
+{
+    int i;
+    char *ap, *ap0;
+    uint64_t component_len;
+    if (!sep) sep = ", ";
+    component_len = 15LL + strlen(sep);
+    if (count >= (INT_MAX - 1)/component_len)
+        return NULL;
+    ap = av_malloc(component_len * count + 1);
+    if (!ap)
+        return NULL;
+    ap0   = ap;
+    ap[0] = '\0';
+    for (i = 0; i < count; i++) {
+        unsigned l = snprintf(ap, component_len, "%f%s", dp[i], sep);
+        if(l >= component_len) {
+            av_free(ap0);
+            return NULL;
+        }
+        ap += l;
+    }
+    ap0[strlen(ap0) - strlen(sep)] = '\0';
+    return ap0;
+}
+
+
+char *ff_tshorts2str(int16_t *sp, int count, const char *sep)
+{
+    int i;
+    char *ap, *ap0;
+    uint64_t component_len;
+    if (!sep) sep = ", ";
+    component_len = 7LL + strlen(sep);
+    if (count >= (INT_MAX - 1)/component_len)
+        return NULL;
+    ap = av_malloc(component_len * count + 1);
+    if (!ap)
+        return NULL;
+    ap0   = ap;
+    ap[0] = '\0';
+    for (i = 0; i < count; i++) {
+        unsigned l = snprintf(ap, component_len, "%d%s", sp[i], sep);
+        if (l >= component_len) {
+            av_free(ap0);
+            return NULL;
+        }
+        ap += l;
+    }
+    ap0[strlen(ap0) - strlen(sep)] = '\0';
+    return ap0;
+}
+
+
+int ff_tadd_doubles_metadata(int count, const char *name, const char *sep,
+                             GetByteContext *gb, int le, AVDictionary **metadata)
+{
+    char *ap;
+    int i;
+    double *dp;
+
+    if (count >= INT_MAX / sizeof(int64_t) || count <= 0)
+        return AVERROR_INVALIDDATA;
+    if (bytestream2_get_bytes_left(gb) < count * sizeof(int64_t))
+        return AVERROR_INVALIDDATA;
+
+    dp = av_malloc(count * sizeof(double));
+    if (!dp)
+        return AVERROR(ENOMEM);
+
+    for (i = 0; i < count; i++)
+        dp[i] = ff_tget_double(gb, le);
+    ap = ff_tdoubles2str(dp, count, sep);
+    av_freep(&dp);
+    if (!ap)
+        return AVERROR(ENOMEM);
+    av_dict_set(metadata, name, ap, AV_DICT_DONT_STRDUP_VAL);
+    return 0;
+}
+
+
+int ff_tadd_shorts_metadata(int count, const char *name, const char *sep,
+                            GetByteContext *gb, int le, AVDictionary **metadata)
+{
+    char *ap;
+    int i;
+    int16_t *sp;
+
+    if (count >= INT_MAX / sizeof(int16_t) || count <= 0)
+        return AVERROR_INVALIDDATA;
+    if (bytestream2_get_bytes_left(gb) < count * sizeof(int16_t))
+        return AVERROR_INVALIDDATA;
+
+    sp = av_malloc(count * sizeof(int16_t));
+    if (!sp)
+        return AVERROR(ENOMEM);
+
+    for (i = 0; i < count; i++)
+        sp[i] = ff_tget_short(gb, le);
+    ap = ff_tshorts2str(sp, count, sep);
+    av_freep(&sp);
+    if (!ap)
+        return AVERROR(ENOMEM);
+    av_dict_set(metadata, name, ap, AV_DICT_DONT_STRDUP_VAL);
+    return 0;
+}
+
+
+int ff_tadd_string_metadata(int count, const char *name,
+                            GetByteContext *gb, int le, AVDictionary **metadata)
+{
+    char *value;
+
+    if (bytestream2_get_bytes_left(gb) < count || count < 0)
+        return AVERROR_INVALIDDATA;
+
+    value = av_malloc(count + 1);
+    if (!value)
+        return AVERROR(ENOMEM);
+
+    bytestream2_get_bufferu(gb, value, count);
+    value[count] = 0;
+
+    av_dict_set(metadata, name, value, AV_DICT_DONT_STRDUP_VAL);
+    return 0;
+}
+
+
+int ff_tdecode_header(GetByteContext *gb, int *le, int *ifd_offset)
+{
+    if (bytestream2_get_bytes_left(gb) < 8) {
+        return AVERROR_INVALIDDATA;
+    }
+
+    *le = bytestream2_get_le16u(gb);
+    if (*le == AV_RB16("II")) {
+        *le = 1;
+    } else if (*le == AV_RB16("MM")) {
+        *le = 0;
+    } else {
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (ff_tget_short(gb, *le) != 42) {
+        return AVERROR_INVALIDDATA;
+    }
+
+    *ifd_offset = ff_tget_long(gb, *le);
+
+    return 0;
+}
+
+
+void ff_tread_tag_data(GetByteContext *gb, int le, unsigned *tag,
+                        unsigned *type, unsigned *count, unsigned *offset)
+{
+    *tag    = ff_tget_short(gb, le);
+    *type   = ff_tget_short(gb, le);
+    *count  = ff_tget_long (gb, le);
+    *offset = ff_tget_long (gb, le);
+}
+
+
+void ff_tseek_tag_value(GetByteContext *gb, unsigned type,
+                         unsigned count, unsigned offset)
+{
+    if (count <= 4 && (type_sizes[type] * count <= 4 || type == TIFF_STRING)) {
+        bytestream2_seek(gb, -4, SEEK_CUR);
+    } else {
+        bytestream2_seek(gb, offset, SEEK_SET);
+    }
+}
+
+
diff --git a/libavcodec/tiff_common.h b/libavcodec/tiff_common.h
new file mode 100644
index 0000000..952ebc1
--- /dev/null
+++ b/libavcodec/tiff_common.h
@@ -0,0 +1,113 @@
+/*
+ * TIFF Common Routines
+ * Copyright (c) 2013 Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * TIFF Common Routines
+ * @author Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
+ */
+
+#ifndef AVCODEC_COMMON_H
+#define AVCODEC_COMMON_H
+
+#include "tiff.h"
+#include "bytestream.h"
+
+/** data type identifiers for TIFF tags */
+enum TiffTypes {
+    TIFF_BYTE = 1,
+    TIFF_STRING,
+    TIFF_SHORT,
+    TIFF_LONG,
+    TIFF_RATIONAL,
+    TIFF_SBYTE,
+    TIFF_UNDEFINED,
+    TIFF_SSHORT,
+    TIFF_SLONG,
+    TIFF_SRATIONAL,
+    TIFF_FLOAT,
+    TIFF_DOUBLE,
+    TIFF_IFD
+};
+
+/** sizes of various TIFF field types (string size = 100)*/
+static const uint8_t type_sizes[14] = {
+    0, 1, 100, 2, 4, 8, 1, 1, 2, 4, 8, 4, 8, 4
+};
+
+/** Read a short from the bytestream using given endianess. */
+unsigned ff_tget_short(GetByteContext *gb, int le);
+
+/** Read a long from the bytestream using given endianess. */
+unsigned ff_tget_long(GetByteContext *gb, int le);
+
+/** Read a double from the bytestream using given endianess. */
+double   ff_tget_double(GetByteContext *gb, int le);
+
+/** Read a byte from the bytestream using given endianess. */
+unsigned ff_tget(GetByteContext *gb, int type, int le);
+
+/** Returns an allocated string containing count
+ *  double values using the given seperator.
+ */
+char *ff_tdoubles2str(double *dp, int count, const char *sep);
+
+/** Returns an allocated string containing count
+ *  short values using the given seperator.
+ */
+char *ff_tshorts2str(int16_t *sp, int count, const char *sep);
+
+/** Adds count doubles converted to a string
+ *  into the metadata dictionary.
+ */
+int ff_tadd_doubles_metadata(int count, const char *name, const char *sep,
+                                    GetByteContext *gb, int le, AVDictionary **metadata);
+
+/** Adds count shorts converted to a string
+ *  into the metadata dictionary.
+ */
+int ff_tadd_shorts_metadata(int count, const char *name, const char *sep,
+                                   GetByteContext *gb, int le, AVDictionary **metadata);
+
+/** Adds a string of count characters
+ *  into the metadata dictionary.
+ */
+int ff_tadd_string_metadata(int count, const char *name,
+                                   GetByteContext *gb, int le, AVDictionary **metadata);
+
+/** Decodes a TIFF header from the input bytestream
+ *  and sets the endianess in *le and the offset to
+ *  the first IFD in *ifd_offset accordingly.
+ */
+int ff_tdecode_header(GetByteContext *gb, int *le, int *ifd_offset);
+
+/** Reads the fixed 12-byte long TIFF tag data.
+ */
+void ff_tread_tag_data(GetByteContext *gb, int le, unsigned *tag,
+                        unsigned *type, unsigned *count, unsigned *offset);
+
+/** Seeks the bytestream to the position of the
+ *  array of values for the given tag data.
+ */
+void ff_tseek_tag_value(GetByteContext *gb, unsigned type,
+                         unsigned count, unsigned offset);
+
+#endif /* AVCODEC_COMMON_H */
-- 
1.7.4.3



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