avcodec/movtextenc: Simplify writing to AVBPrint

The mov_text encoder uses an AVBPrint to assemble the subtitles;
yet mov_text subtitles are not pure text; they also have a binary
portion that was mostly handled as follows:

    uint32_t size = /* calculation */;
    size = AV_RB32(&size);
    av_bprint_append_data(bprint, (const char*)&size, 4);

Here AV_RB32() is a no-op on big-endian systems and a LE-BE swap
on little-endian systems, making the output endian-independent.

Yet this is ugly and unclean: On LE systems, the variable size from
the snippet above won't contain the correct value any more. Furthermore,
using this pattern leads to lots of small writes to the AVBPrint.

This commit therefore changes this to using a temporary buffer instead:

    uint8_t buf[4];
    AV_WB32(buf, /* size calculation */);
    av_bprint_append_data(bprint, buf, 4);

This method also allows to use bigger buffers holding more than one
element, saving calls to av_bprint_append_data() and reducing codesize.

Reviewed-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

1 files changed, 66 insertions, 87 deletions

diff --git a/libavcodec/movtextenc.c b/libavcodec/movtextenc.c
index 42fdf98042..908b2bfde5 100644
--- a/libavcodec/movtextenc.c
+++ b/libavcodec/movtextenc.c
@@ -29,6 +29,7 @@
 #include "libavutil/common.h"
 #include "ass_split.h"
 #include "ass.h"
+#include "bytestream.h"
 
 #define STYLE_FLAG_BOLD         (1<<0)
 #define STYLE_FLAG_ITALIC       (1<<1)
@@ -103,33 +104,27 @@ static void mov_text_cleanup(MovTextContext *s)
 
 static void encode_styl(MovTextContext *s, uint32_t tsmb_type)
 {
-    uint32_t tsmb_size;
-    uint16_t style_entries;
     if ((s->box_flags & STYL_BOX) && s->count) {
-        tsmb_size = s->count * STYLE_RECORD_SIZE + SIZE_ADD;
-        tsmb_size = AV_RB32(&tsmb_size);
-        tsmb_type = AV_RB32(&tsmb_type);
-        style_entries = AV_RB16(&s->count);
+        uint8_t buf[12], *p = buf;
+
+        bytestream_put_be32(&p, s->count * STYLE_RECORD_SIZE + SIZE_ADD);
+        bytestream_put_be32(&p, tsmb_type);
+        bytestream_put_be16(&p, s->count);
         /*The above three attributes are hard coded for now
         but will come from ASS style in the future*/
-        av_bprint_append_any(&s->buffer, &tsmb_size, 4);
-        av_bprint_append_any(&s->buffer, &tsmb_type, 4);
-        av_bprint_append_any(&s->buffer, &style_entries, 2);
+        av_bprint_append_any(&s->buffer, buf, 10);
         for (unsigned j = 0; j < s->count; j++) {
-            uint16_t style_start, style_end, style_fontID;
-            uint32_t style_color;
-
-            style_start  = AV_RB16(&s->style_attributes[j].style_start);
-            style_end    = AV_RB16(&s->style_attributes[j].style_end);
-            style_color  = AV_RB32(&s->style_attributes[j].style_color);
-            style_fontID = AV_RB16(&s->style_attributes[j].style_fontID);
-
-            av_bprint_append_any(&s->buffer, &style_start, 2);
-            av_bprint_append_any(&s->buffer, &style_end, 2);
-            av_bprint_append_any(&s->buffer, &style_fontID, 2);
-            av_bprint_append_any(&s->buffer, &s->style_attributes[j].style_flag, 1);
-            av_bprint_append_any(&s->buffer, &s->style_attributes[j].style_fontsize, 1);
-            av_bprint_append_any(&s->buffer, &style_color, 4);
+            const StyleBox *style = &s->style_attributes[j];
+
+            p = buf;
+            bytestream_put_be16(&p, style->style_start);
+            bytestream_put_be16(&p, style->style_end);
+            bytestream_put_be16(&p, style->style_fontID);
+            bytestream_put_byte(&p, style->style_flag);
+            bytestream_put_byte(&p, style->style_fontsize);
+            bytestream_put_be32(&p, style->style_color);
+
+            av_bprint_append_any(&s->buffer, buf, 12);
         }
     }
     mov_text_cleanup(s);
@@ -137,32 +132,28 @@ static void encode_styl(MovTextContext *s, uint32_t tsmb_type)
 
 static void encode_hlit(MovTextContext *s, uint32_t tsmb_type)
 {
-    uint32_t tsmb_size;
-    uint16_t start, end;
     if (s->box_flags & HLIT_BOX) {
-        tsmb_size = 12;
-        tsmb_size = AV_RB32(&tsmb_size);
-        tsmb_type = AV_RB32(&tsmb_type);
-        start     = AV_RB16(&s->hlit.start);
-        end       = AV_RB16(&s->hlit.end);
-        av_bprint_append_any(&s->buffer, &tsmb_size, 4);
-        av_bprint_append_any(&s->buffer, &tsmb_type, 4);
-        av_bprint_append_any(&s->buffer, &start, 2);
-        av_bprint_append_any(&s->buffer, &end, 2);
+        uint8_t buf[12], *p = buf;
+
+        bytestream_put_be32(&p, 12);
+        bytestream_put_be32(&p, tsmb_type);
+        bytestream_put_be16(&p, s->hlit.start);
+        bytestream_put_be16(&p, s->hlit.end);
+
+        av_bprint_append_any(&s->buffer, buf, 12);
     }
 }
 
 static void encode_hclr(MovTextContext *s, uint32_t tsmb_type)
 {
-    uint32_t tsmb_size, color;
     if (s->box_flags & HCLR_BOX) {
-        tsmb_size = 12;
-        tsmb_size = AV_RB32(&tsmb_size);
-        tsmb_type = AV_RB32(&tsmb_type);
-        color     = AV_RB32(&s->hclr.color);
-        av_bprint_append_any(&s->buffer, &tsmb_size, 4);
-        av_bprint_append_any(&s->buffer, &tsmb_type, 4);
-        av_bprint_append_any(&s->buffer, &color, 4);
+        uint8_t buf[12], *p = buf;
+
+        bytestream_put_be32(&p, 12);
+        bytestream_put_be32(&p, tsmb_type);
+        bytestream_put_be32(&p, s->hclr.color);
+
+        av_bprint_append_any(&s->buffer, buf, 12);
     }
 }
 
@@ -190,25 +181,21 @@ static int encode_sample_description(AVCodecContext *avctx)
     ASS *ass;
     ASSStyle *style;
     int i, j;
-    uint32_t tsmb_size, tsmb_type, back_color = 0, style_color;
-    uint16_t style_start, style_end, fontID, count;
+    uint32_t back_color = 0;
     int font_names_total_len = 0;
     MovTextContext *s = avctx->priv_data;
+    uint8_t buf[30], *p = buf;
 
-    static const uint8_t display_and_justification[] = {
-        0x00, 0x00, 0x00, 0x00, // uint32_t displayFlags
-        0x01,                   // int8_t horizontal-justification
-        0xFF,                   // int8_t vertical-justification
-    };
+    //  0x00, 0x00, 0x00, 0x00, // uint32_t displayFlags
+    //  0x01,                   // int8_t horizontal-justification
+    //  0xFF,                   // int8_t vertical-justification
     //  0x00, 0x00, 0x00, 0x00, // uint8_t background-color-rgba[4]
-    static const uint8_t box_record[] = {
     //     BoxRecord {
-        0x00, 0x00,             // int16_t top
-        0x00, 0x00,             // int16_t left
-        0x00, 0x00,             // int16_t bottom
-        0x00, 0x00,             // int16_t right
+    //  0x00, 0x00,             // int16_t top
+    //  0x00, 0x00,             // int16_t left
+    //  0x00, 0x00,             // int16_t bottom
+    //  0x00, 0x00,             // int16_t right
     //     };
-    };
     //     StyleRecord {
     //  0x00, 0x00,             // uint16_t startChar
     //  0x00, 0x00,             // uint16_t endChar
@@ -256,25 +243,19 @@ static int encode_sample_description(AVCodecContext *avctx)
                      (255 - ((uint32_t)style->back_color >> 24));
     }
 
-    av_bprint_append_any(&s->buffer, display_and_justification,
-                                     sizeof(display_and_justification));
-    back_color = AV_RB32(&back_color);
-    av_bprint_append_any(&s->buffer, &back_color, 4);
-    //     BoxRecord {
-    av_bprint_append_any(&s->buffer, box_record, sizeof(box_record));
-    //     };
+    bytestream_put_be32(&p, 0); // displayFlags
+    bytestream_put_be16(&p, 0x01FF); // horizontal/vertical justification (2x int8_t)
+    bytestream_put_be32(&p, back_color);
+    bytestream_put_be64(&p, 0); // BoxRecord - 4xint16_t: top, left, bottom, right
     //     StyleRecord {
-    style_start  = AV_RB16(&s->d.style_start);
-    style_end    = AV_RB16(&s->d.style_end);
-    fontID = AV_RB16(&s->d.style_fontID);
-    style_color  = AV_RB32(&s->d.style_color);
-    av_bprint_append_any(&s->buffer, &style_start, 2);
-    av_bprint_append_any(&s->buffer, &style_end, 2);
-    av_bprint_append_any(&s->buffer, &fontID, 2);
-    av_bprint_append_any(&s->buffer, &s->d.style_flag, 1);
-    av_bprint_append_any(&s->buffer, &s->d.style_fontsize, 1);
-    av_bprint_append_any(&s->buffer, &style_color, 4);
+    bytestream_put_be16(&p, s->d.style_start);
+    bytestream_put_be16(&p, s->d.style_end);
+    bytestream_put_be16(&p, s->d.style_fontID);
+    bytestream_put_byte(&p, s->d.style_flag);
+    bytestream_put_byte(&p, s->d.style_fontsize);
+    bytestream_put_be32(&p, s->d.style_color);
     //     };
+    av_bprint_append_any(&s->buffer, buf, 30);
 
     // Build font table
     // We can't build a complete font table since that would require
@@ -306,23 +287,21 @@ static int encode_sample_description(AVCodecContext *avctx)
         av_dynarray_add(&s->fonts, &s->font_count, (char*)"Serif");
 
     //     FontTableBox {
-    tsmb_size = SIZE_ADD + 3 * s->font_count + font_names_total_len;
-    tsmb_size = AV_RB32(&tsmb_size);
-    tsmb_type = MKBETAG('f','t','a','b');
-    tsmb_type = AV_RB32(&tsmb_type);
-    count = s->font_count;
-    count = AV_RB16(&count);
-    av_bprint_append_any(&s->buffer, &tsmb_size, 4);
-    av_bprint_append_any(&s->buffer, &tsmb_type, 4);
-    av_bprint_append_any(&s->buffer, &count, 2);
+    p = buf;
+    bytestream_put_be32(&p, SIZE_ADD + 3 * s->font_count + font_names_total_len); // Size
+    bytestream_put_be32(&p, MKBETAG('f','t','a','b'));
+    bytestream_put_be16(&p, s->font_count);
+
+    av_bprint_append_any(&s->buffer, buf, 10);
     //     FontRecord {
     for (i = 0; i < s->font_count; i++) {
-        uint8_t len;
-        fontID = i + 1;
-        fontID = AV_RB16(&fontID);
-        av_bprint_append_any(&s->buffer, &fontID, 2);
-        len = strlen(s->fonts[i]);
-        av_bprint_append_any(&s->buffer, &len, 1);
+        size_t len = strlen(s->fonts[i]);
+
+        p = buf;
+        bytestream_put_be16(&p, i + 1); //fontID
+        bytestream_put_byte(&p, len);
+
+        av_bprint_append_any(&s->buffer, buf, 3);
         av_bprint_append_any(&s->buffer, s->fonts[i], len);
     }
     //     };