avformat/mxfdec: Fix av_log context

Fixes: out of array access
Fixes: mxf-crash-1c2e59bf07a34675bfb3ada5e1ec22fa9f38f923

Found-by: Paul Ch <paulcher@icloud.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_table, int64_t edit_unit, AVRational edit_rate, int64_t *edit_unit_out, int64_t *offset_out, MXFPartition **partition_out, int nag)
{
    int i;
    int64_t offset_temp = 0;

    edit_unit = av_rescale_q(edit_unit, index_table->segments[0]->index_edit_rate, edit_rate);

    for (i = 0; i < index_table->nb_segments; i++) {
        MXFIndexTableSegment *s = index_table->segments[i];

        edit_unit = FFMAX(edit_unit, s->index_start_position);  /* clamp if trying to seek before start */

        if (edit_unit < s->index_start_position + s->index_duration) {
            int64_t index = edit_unit - s->index_start_position;

            if (s->edit_unit_byte_count)
                offset_temp += s->edit_unit_byte_count * index;
            else if (s->nb_index_entries) {
                if (s->nb_index_entries == 2 * s->index_duration + 1)
                    index *= 2;     /* Avid index */

                if (index < 0 || index >= s->nb_index_entries) {
                    av_log(mxf->fc, AV_LOG_ERROR, "IndexSID %i segment at %"PRId64" IndexEntryArray too small\n",
                           index_table->index_sid, s->index_start_position);
                    return AVERROR_INVALIDDATA;
                }

                offset_temp = s->stream_offset_entries[index];
            } else {
                av_log(mxf->fc, AV_LOG_ERROR, "IndexSID %i segment at %"PRId64" missing EditUnitByteCount and IndexEntryArray\n",
                       index_table->index_sid, s->index_start_position);
                return AVERROR_INVALIDDATA;
            }

            if (edit_unit_out)
                *edit_unit_out = av_rescale_q(edit_unit, edit_rate, s->index_edit_rate);

            return mxf_absolute_bodysid_offset(mxf, index_table->body_sid, offset_temp, offset_out, partition_out);
        } else {
            /* EditUnitByteCount == 0 for VBR indexes, which is fine since they use explicit StreamOffsets */
            offset_temp += s->edit_unit_byte_count * s->index_duration;
        }
    }

    if (nag)
        av_log(mxf->fc, AV_LOG_ERROR, "failed to map EditUnit %"PRId64" in IndexSID %i to an offset\n", edit_unit, index_table->index_sid);

    return AVERROR_INVALIDDATA;
}

static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_table, int64_t edit_unit, AVRational edit_rate, int64_t *edit_unit_out, int64_t *offset_out, MXFPartition **partition_out, int nag)
{
    int i;
    int64_t offset_temp = 0;

    edit_unit = av_rescale_q(edit_unit, index_table->segments[0]->index_edit_rate, edit_rate);

    for (i = 0; i < index_table->nb_segments; i++) {
        MXFIndexTableSegment *s = index_table->segments[i];

        edit_unit = FFMAX(edit_unit, s->index_start_position);  /* clamp if trying to seek before start */

        if (edit_unit < s->index_start_position + s->index_duration) {
            int64_t index = edit_unit - s->index_start_position;

            if (s->edit_unit_byte_count)
                offset_temp += s->edit_unit_byte_count * index;
            else if (s->nb_index_entries) {
                if (s->nb_index_entries == 2 * s->index_duration + 1)
                    index *= 2;     /* Avid index */

                if (index < 0 || index >= s->nb_index_entries) {
                    av_log(mxf->fc, AV_LOG_ERROR, "IndexSID %i segment at %"PRId64" IndexEntryArray too small\n",
                           index_table->index_sid, s->index_start_position);
                    return AVERROR_INVALIDDATA;
                }

                offset_temp = s->stream_offset_entries[index];
            } else {
                av_log(mxf->fc, AV_LOG_ERROR, "IndexSID %i segment at %"PRId64" missing EditUnitByteCount and IndexEntryArray\n",
                       index_table->index_sid, s->index_start_position);
                return AVERROR_INVALIDDATA;
            }

            if (edit_unit_out)
                *edit_unit_out = av_rescale_q(edit_unit, edit_rate, s->index_edit_rate);

            return mxf_absolute_bodysid_offset(mxf, index_table->body_sid, offset_temp, offset_out, partition_out);
        } else {
            /* EditUnitByteCount == 0 for VBR indexes, which is fine since they use explicit StreamOffsets */
            offset_temp += s->edit_unit_byte_count * s->index_duration;
        }
    }

    if (nag)
        av_log(mxf->fc, AV_LOG_ERROR, "failed to map EditUnit %"PRId64" in IndexSID %i to an offset\n", edit_unit, index_table->index_sid);

    return AVERROR_INVALIDDATA;
}
