avformat: split off generic NAL function helpers into their own file

Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 190 insertions, 0 deletions

diff --git a/libavformat/nal.c b/libavformat/nal.c
new file mode 100644
index 0000000000..26dc5fe688
--- /dev/null
+++ b/libavformat/nal.c
@@ -0,0 +1,190 @@
+/*
+ * NAL helper functions for muxers
+ *
+ * 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
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include "libavutil/mem.h"
+#include "libavutil/error.h"
+#include "libavcodec/defs.h"
+#include "avio.h"
+#include "avio_internal.h"
+#include "nal.h"
+
+static const uint8_t *nal_find_startcode_internal(const uint8_t *p, const uint8_t *end)
+{
+    const uint8_t *a = p + 4 - ((intptr_t)p & 3);
+
+    for (end -= 3; p < a && p < end; p++) {
+        if (p[0] == 0 && p[1] == 0 && p[2] == 1)
+            return p;
+    }
+
+    for (end -= 3; p < end; p += 4) {
+        uint32_t x = *(const uint32_t*)p;
+//      if ((x - 0x01000100) & (~x) & 0x80008000) // little endian
+//      if ((x - 0x00010001) & (~x) & 0x00800080) // big endian
+        if ((x - 0x01010101) & (~x) & 0x80808080) { // generic
+            if (p[1] == 0) {
+                if (p[0] == 0 && p[2] == 1)
+                    return p;
+                if (p[2] == 0 && p[3] == 1)
+                    return p+1;
+            }
+            if (p[3] == 0) {
+                if (p[2] == 0 && p[4] == 1)
+                    return p+2;
+                if (p[4] == 0 && p[5] == 1)
+                    return p+3;
+            }
+        }
+    }
+
+    for (end += 3; p < end; p++) {
+        if (p[0] == 0 && p[1] == 0 && p[2] == 1)
+            return p;
+    }
+
+    return end + 3;
+}
+
+const uint8_t *ff_nal_find_startcode(const uint8_t *p, const uint8_t *end){
+    const uint8_t *out = nal_find_startcode_internal(p, end);
+    if(p<out && out<end && !out[-1]) out--;
+    return out;
+}
+
+static int nal_parse_units(AVIOContext *pb, NALUList *list,
+                           const uint8_t *buf_in, int size)
+{
+    const uint8_t *p = buf_in;
+    const uint8_t *end = p + size;
+    const uint8_t *nal_start, *nal_end;
+
+    size = 0;
+    nal_start = ff_nal_find_startcode(p, end);
+    for (;;) {
+        const size_t nalu_limit = SIZE_MAX / sizeof(*list->nalus);
+        while (nal_start < end && !*(nal_start++));
+        if (nal_start == end)
+            break;
+
+        nal_end = ff_nal_find_startcode(nal_start, end);
+        if (pb) {
+            avio_wb32(pb, nal_end - nal_start);
+            avio_write(pb, nal_start, nal_end - nal_start);
+        } else if (list->nb_nalus >= nalu_limit) {
+            return AVERROR(ERANGE);
+        } else {
+            NALU *tmp = av_fast_realloc(list->nalus, &list->nalus_array_size,
+                                        (list->nb_nalus + 1) * sizeof(*list->nalus));
+            if (!tmp)
+                return AVERROR(ENOMEM);
+            list->nalus = tmp;
+            tmp[list->nb_nalus++] = (NALU){ .offset = nal_start - p,
+                                            .size   = nal_end - nal_start };
+        }
+        size += 4 + nal_end - nal_start;
+        nal_start = nal_end;
+    }
+    return size;
+}
+
+int ff_nal_parse_units(AVIOContext *pb, const uint8_t *buf_in, int size)
+{
+    return nal_parse_units(pb, NULL, buf_in, size);
+}
+
+int ff_nal_units_create_list(NALUList *list, const uint8_t *buf, int size)
+{
+    list->nb_nalus = 0;
+    return nal_parse_units(NULL, list, buf, size);
+}
+
+void ff_nal_units_write_list(const NALUList *list, AVIOContext *pb,
+                             const uint8_t *buf)
+{
+    for (unsigned i = 0; i < list->nb_nalus; i++) {
+        avio_wb32(pb, list->nalus[i].size);
+        avio_write(pb, buf + list->nalus[i].offset, list->nalus[i].size);
+    }
+}
+
+int ff_nal_parse_units_buf(const uint8_t *buf_in, uint8_t **buf, int *size)
+{
+    AVIOContext *pb;
+    int ret = avio_open_dyn_buf(&pb);
+    if(ret < 0)
+        return ret;
+
+    ff_nal_parse_units(pb, buf_in, *size);
+
+    *size = avio_close_dyn_buf(pb, buf);
+    return 0;
+}
+
+const uint8_t *ff_nal_mp4_find_startcode(const uint8_t *start,
+                                         const uint8_t *end,
+                                         int nal_length_size)
+{
+    unsigned int res = 0;
+
+    if (end - start < nal_length_size)
+        return NULL;
+    while (nal_length_size--)
+        res = (res << 8) | *start++;
+
+    if (res > end - start)
+        return NULL;
+
+    return start + res;
+}
+
+uint8_t *ff_nal_unit_extract_rbsp(const uint8_t *src, uint32_t src_len,
+                                  uint32_t *dst_len, int header_len)
+{
+    uint8_t *dst;
+    uint32_t i, len;
+
+    dst = av_malloc(src_len + AV_INPUT_BUFFER_PADDING_SIZE);
+    if (!dst)
+        return NULL;
+
+    /* NAL unit header */
+    i = len = 0;
+    while (i < header_len && i < src_len)
+        dst[len++] = src[i++];
+
+    while (i + 2 < src_len)
+        if (!src[i] && !src[i + 1] && src[i + 2] == 3) {
+            dst[len++] = src[i++];
+            dst[len++] = src[i++];
+            i++; // remove emulation_prevention_three_byte
+        } else
+            dst[len++] = src[i++];
+
+    while (i < src_len)
+        dst[len++] = src[i++];
+
+    memset(dst + len, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+    *dst_len = len;
+    return dst;
+}