avcodec/tiff: Refactor TIFF tag related functions to share the code.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

5 files changed, 457 insertions, 203 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 5c8f9d5ed5..5ba8a1ab9e 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -426,7 +426,7 @@ 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 2e06e3ff0e..ac7ac6016e 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;
@@ -245,111 +213,13 @@ static char *doubles2str(double *dp, int count, const char *sep)
     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;
     };
 }
@@ -702,14 +572,8 @@ 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);
-    start = bytestream2_tell(&s->gb) + 4;
-
-    if (type == 0 || type >= FF_ARRAY_ELEMS(type_sizes)) {
-        av_log(s->avctx, AV_LOG_DEBUG, "Unknown tiff type (%u) encountered\n",
-               type);
+    ret = ff_tread_tag(&s->gb, s->le, &tag, &type, &count, &start);
+    if (ret < 0) {
         goto end;
     }
 
@@ -717,10 +581,10 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
         switch (type) {
         case TIFF_BYTE:
         case TIFF_SHORT:
-            value = tget(&s->gb, type, s->le);
+            value = ff_tget(&s->gb, type, s->le);
             break;
         case TIFF_LONG:
-            off   = tget_long(&s->gb, s->le);
+            off   = ff_tget_long(&s->gb, s->le);
             value = off;
             break;
         case TIFF_STRING:
@@ -728,14 +592,12 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
                 break;
             }
         default:
-            off   = tget_long(&s->gb, s->le);
+            off   = bytestream2_tell(&s->gb);
             value = UINT_MAX;
-            bytestream2_seek(&s->gb, off, SEEK_SET);
         }
     } else {
         if (type_sizes[type] * count > 4) {
-            off   = tget_long(&s->gb, s->le);
-            bytestream2_seek(&s->gb, off, SEEK_SET);
+            off   = bytestream2_tell(&s->gb);
         }
     }
 
@@ -768,7 +630,7 @@ 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;
@@ -908,7 +770,7 @@ 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;
             }
         }
@@ -942,7 +804,7 @@ 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");
@@ -958,14 +820,14 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             goto end;
         }
         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:
@@ -979,7 +841,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             goto end;
         }
         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
@@ -1075,7 +937,7 @@ 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 +947,11 @@ 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 +962,11 @@ 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 +1026,12 @@ 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 3ea2158033..ae189b6fdd 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 0000000000..0995daea81
--- /dev/null
+++ b/libavcodec/tiff_common.c
@@ -0,0 +1,282 @@
+/*
+ * 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"
+
+
+int ff_tis_ifd(unsigned tag)
+{
+    int i;
+    for (i = 0; i < FF_ARRAY_ELEMS(ifd_tags); i++) {
+        if (ifd_tags[i] == tag) {
+            return i + 1;
+        }
+    }
+    return 0;
+}
+
+
+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;
+    }
+}
+
+
+int ff_tadd_rational_metadata(int count, const char *name, const char *sep,
+                              GetByteContext *gb, int le, AVDictionary **metadata)
+{
+    AVBPrint bp;
+    char *ap;
+    int32_t nom, denom;
+    int i;
+
+    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;
+    if (!sep) sep = ", ";
+
+    av_bprint_init(&bp, 10 * count, AV_BPRINT_SIZE_AUTOMATIC);
+
+    for (i = 0; i < count; i++) {
+        nom   = ff_tget_long(gb, le);
+        denom = ff_tget_long(gb, le);
+        av_bprintf(&bp, "%s%i:%i", (i ? sep : ""), nom, denom);
+    }
+
+    if ((i = av_bprint_finalize(&bp, &ap))) {
+        return i;
+    }
+    if (!ap) {
+        return AVERROR(ENOMEM);
+    }
+
+    av_dict_set(metadata, name, ap, AV_DICT_DONT_STRDUP_VAL);
+
+    return 0;
+}
+
+
+int ff_tadd_long_metadata(int count, const char *name, const char *sep,
+                          GetByteContext *gb, int le, AVDictionary **metadata)
+{
+    AVBPrint bp;
+    char *ap;
+    int i;
+
+    if (count >= INT_MAX / sizeof(int32_t) || count <= 0)
+        return AVERROR_INVALIDDATA;
+    if (bytestream2_get_bytes_left(gb) < count * sizeof(int32_t))
+        return AVERROR_INVALIDDATA;
+    if (!sep) sep = ", ";
+
+    av_bprint_init(&bp, 10 * count, AV_BPRINT_SIZE_AUTOMATIC);
+
+    for (i = 0; i < count; i++) {
+        av_bprintf(&bp, "%s%i", (i ? sep : ""), ff_tget_long(gb, le));
+    }
+
+    if ((i = av_bprint_finalize(&bp, &ap))) {
+        return i;
+    }
+    if (!ap) {
+        return AVERROR(ENOMEM);
+    }
+
+    av_dict_set(metadata, name, ap, AV_DICT_DONT_STRDUP_VAL);
+
+    return 0;
+}
+
+
+int ff_tadd_doubles_metadata(int count, const char *name, const char *sep,
+                             GetByteContext *gb, int le, AVDictionary **metadata)
+{
+    AVBPrint bp;
+    char *ap;
+    int i;
+
+    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;
+    if (!sep) sep = ", ";
+
+    av_bprint_init(&bp, 10 * count, AV_BPRINT_SIZE_AUTOMATIC);
+
+    for (i = 0; i < count; i++) {
+        av_bprintf(&bp, "%s%f", (i ? sep : ""), ff_tget_double(gb, le));
+    }
+
+    if ((i = av_bprint_finalize(&bp, &ap))) {
+        return i;
+    }
+    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)
+{
+    AVBPrint bp;
+    char *ap;
+    int i;
+
+    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;
+    if (!sep) sep = ", ";
+
+    av_bprint_init(&bp, 10 * count, AV_BPRINT_SIZE_AUTOMATIC);
+
+    for (i = 0; i < count; i++) {
+        av_bprintf(&bp, "%s%i", (i ? sep : ""), ff_tget_short(gb, le));
+    }
+
+    if ((i = av_bprint_finalize(&bp, &ap))) {
+        return i;
+    }
+    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;
+}
+
+
+int ff_tread_tag(GetByteContext *gb, int le, unsigned *tag, unsigned *type,
+                 unsigned *count, int *next)
+{
+    int ifd_tag;
+    int valid_type;
+
+    *tag    = ff_tget_short(gb, le);
+    *type   = ff_tget_short(gb, le);
+    *count  = ff_tget_long (gb, le);
+
+    ifd_tag    = ff_tis_ifd(*tag);
+    valid_type = *type != 0 && *type < FF_ARRAY_ELEMS(type_sizes);
+
+    *next = bytestream2_tell(gb) + 4;
+
+    // check for valid type
+    if (!valid_type) {
+        return AVERROR_INVALIDDATA;
+    }
+
+    // seek to offset if this is an IFD-tag or
+    // if count values do not fit into the offset value
+    if (ifd_tag || (*count > 4 || !(type_sizes[*type] * (*count) <= 4 || *type == TIFF_STRING))) {
+        bytestream2_seek(gb, ff_tget_long (gb, le), SEEK_SET);
+    }
+
+    return 0;
+}
diff --git a/libavcodec/tiff_common.h b/libavcodec/tiff_common.h
new file mode 100644
index 0000000000..15eeb76df6
--- /dev/null
+++ b/libavcodec/tiff_common.h
@@ -0,0 +1,146 @@
+/*
+ * 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_TIFF_COMMON_H
+#define AVCODEC_TIFF_COMMON_H
+
+#include "avcodec.h"
+#include "tiff.h"
+#include "bytestream.h"
+#include "libavutil/bprint.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
+};
+
+static const uint16_t ifd_tags[] = {
+    0x8769, // EXIF IFD
+    0x8825, // GPS IFD
+    0xA005  // Interoperability IFD
+};
+
+
+/** Returns a value > 0 if the tag is a known IFD-tag.
+ *  The return value is the array index + 1 within ifd_tags[].
+ */
+int ff_tis_ifd(unsigned tag);
+
+/** Reads a short from the bytestream using given endianess. */
+unsigned ff_tget_short(GetByteContext *gb, int le);
+
+/** Reads a long from the bytestream using given endianess. */
+unsigned ff_tget_long(GetByteContext *gb, int le);
+
+/** Reads a double from the bytestream using given endianess. */
+double   ff_tget_double(GetByteContext *gb, int le);
+
+/** Reads a byte from the bytestream using given endianess. */
+unsigned ff_tget(GetByteContext *gb, int type, int le);
+
+/** Returns an allocated string containing count
+ *  rational values using the given seperator.
+ */
+char *ff_trationals2str(int *rp, int count, const char *sep);
+
+/** Returns an allocated string containing count
+ *  long values using the given seperator.
+ */
+char *ff_tlongs2str(int32_t *lp, int count, const char *sep);
+
+/** 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 rationals converted to a string
+ *  into the metadata dictionary.
+ */
+int ff_tadd_rational_metadata(int count, const char *name, const char *sep,
+                              GetByteContext *gb, int le, AVDictionary **metadata);
+
+/** Adds count longs converted to a string
+ *  into the metadata dictionary.
+ */
+int ff_tadd_long_metadata(int count, const char *name, const char *sep,
+                          GetByteContext *gb, int le, AVDictionary **metadata);
+
+/** 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 first 3 fields of a TIFF tag, which are
+ *  the tag id, the tag type and the count of values for that tag.
+ *  Afterwards the bytestream is located at the first value to read and
+ *  *next holds the bytestream offset of the following tag.
+ */
+int ff_tread_tag(GetByteContext *gb, int le, unsigned *tag, unsigned *type,
+                 unsigned *count, int *next);
+
+#endif /* AVCODEC_TIFF_COMMON_H */