avcodec/cbs: Factor out common code for writing units

All cbs-functions to write units share a common pattern:
1. They check whether they have a write buffer (that is used to store
the unit's data until the needed size becomes known after writing the
unit when a dedicated buffer will be allocated).
2. They use this buffer for a PutBitContext.
3. The (codec-specific) writing takes place through the PutBitContext.
4. The return value is checked. AVERROR(ENOSPC) here always indicates
that the buffer was too small and leads to a reallocation of said
buffer.
5. The final buffer will be allocated and the data copied.

This commit factors this common code out in a single function in cbs.c.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

1 files changed, 2 insertions, 65 deletions

diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
index 5dd371153a..923f77dcb4 100644
--- a/libavcodec/cbs_h2645.c
+++ b/libavcodec/cbs_h2645.c
@@ -1380,65 +1380,6 @@ static int cbs_h265_write_nal_unit(CodedBitstreamContext *ctx,
     return 0;
 }
 
-static int cbs_h2645_write_nal_unit(CodedBitstreamContext *ctx,
-                                    CodedBitstreamUnit *unit)
-{
-    CodedBitstreamH2645Context *priv = ctx->priv_data;
-    enum AVCodecID codec_id = ctx->codec->codec_id;
-    PutBitContext pbc;
-    int err;
-
-    if (!priv->write_buffer) {
-        // Initial write buffer size is 1MB.
-        priv->write_buffer_size = 1024 * 1024;
-
-    reallocate_and_try_again:
-        err = av_reallocp(&priv->write_buffer, priv->write_buffer_size);
-        if (err < 0) {
-            av_log(ctx->log_ctx, AV_LOG_ERROR, "Unable to allocate a "
-                   "sufficiently large write buffer (last attempt "
-                   "%"SIZE_SPECIFIER" bytes).\n", priv->write_buffer_size);
-            return err;
-        }
-    }
-
-    init_put_bits(&pbc, priv->write_buffer, priv->write_buffer_size);
-
-    if (codec_id == AV_CODEC_ID_H264)
-        err = cbs_h264_write_nal_unit(ctx, unit, &pbc);
-    else
-        err = cbs_h265_write_nal_unit(ctx, unit, &pbc);
-
-    if (err == AVERROR(ENOSPC)) {
-        // Overflow.
-        priv->write_buffer_size *= 2;
-        goto reallocate_and_try_again;
-    }
-    // Overflow but we didn't notice.
-    av_assert0(put_bits_count(&pbc) <= 8 * priv->write_buffer_size);
-
-    if (err < 0) {
-        // Write failed for some other reason.
-        return err;
-    }
-
-    if (put_bits_count(&pbc) % 8)
-        unit->data_bit_padding = 8 - put_bits_count(&pbc) % 8;
-    else
-        unit->data_bit_padding = 0;
-
-    unit->data_size = (put_bits_count(&pbc) + 7) / 8;
-    flush_put_bits(&pbc);
-
-    err = ff_cbs_alloc_unit_data(ctx, unit, unit->data_size);
-    if (err < 0)
-        return err;
-
-    memcpy(unit->data, priv->write_buffer, unit->data_size);
-
-    return 0;
-}
-
 static int cbs_h2645_assemble_fragment(CodedBitstreamContext *ctx,
                                        CodedBitstreamFragment *frag)
 {
@@ -1533,8 +1474,6 @@ static void cbs_h264_close(CodedBitstreamContext *ctx)
 
     ff_h2645_packet_uninit(&h264->common.read_packet);
 
-    av_freep(&h264->common.write_buffer);
-
     for (i = 0; i < FF_ARRAY_ELEMS(h264->sps); i++)
         av_buffer_unref(&h264->sps_ref[i]);
     for (i = 0; i < FF_ARRAY_ELEMS(h264->pps); i++)
@@ -1548,8 +1487,6 @@ static void cbs_h265_close(CodedBitstreamContext *ctx)
 
     ff_h2645_packet_uninit(&h265->common.read_packet);
 
-    av_freep(&h265->common.write_buffer);
-
     for (i = 0; i < FF_ARRAY_ELEMS(h265->vps); i++)
         av_buffer_unref(&h265->vps_ref[i]);
     for (i = 0; i < FF_ARRAY_ELEMS(h265->sps); i++)
@@ -1565,7 +1502,7 @@ const CodedBitstreamType ff_cbs_type_h264 = {
 
     .split_fragment    = &cbs_h2645_split_fragment,
     .read_unit         = &cbs_h264_read_nal_unit,
-    .write_unit        = &cbs_h2645_write_nal_unit,
+    .write_unit        = &cbs_h264_write_nal_unit,
     .assemble_fragment = &cbs_h2645_assemble_fragment,
 
     .close             = &cbs_h264_close,
@@ -1578,7 +1515,7 @@ const CodedBitstreamType ff_cbs_type_h265 = {
 
     .split_fragment    = &cbs_h2645_split_fragment,
     .read_unit         = &cbs_h265_read_nal_unit,
-    .write_unit        = &cbs_h2645_write_nal_unit,
+    .write_unit        = &cbs_h265_write_nal_unit,
     .assemble_fragment = &cbs_h2645_assemble_fragment,
 
     .close             = &cbs_h265_close,