205 lines
7.1 KiB
Go
205 lines
7.1 KiB
Go
package files
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import (
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"bytes"
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"encoding/binary"
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"testing"
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)
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// box 构造一个 MP4 box：[size(4)][type(4)][payload]。
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func box(typ string, payload []byte) []byte {
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b := make([]byte, 8+len(payload))
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binary.BigEndian.PutUint32(b[0:4], uint32(8+len(payload)))
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copy(b[4:8], typ)
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copy(b[8:], payload)
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return b
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}
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// stcoBox 构造一个含单个 chunk 偏移的 stco：[ver+flags(4)][count(4)=1][offset(4)]。
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func stcoBox(offset uint32) []byte {
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p := make([]byte, 12)
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binary.BigEndian.PutUint32(p[4:8], 1) // entry_count
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binary.BigEndian.PutUint32(p[8:12], offset)
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return box("stco", p)
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}
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// buildMoovEndMP4 构造一个 moov 在末尾、stco 指向 mdat 内某偏移的最小合法 MP4。
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// 返回 (mp4, mdatPayloadAbsOffset)。
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func buildMoovEndMP4(mdatPayload []byte) ([]byte, uint32) {
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ftyp := box("ftyp", []byte("isom\x00\x00\x02\x00"))
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mdat := box("mdat", mdatPayload)
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mdatAbs := uint32(len(ftyp) + 8) // mdat payload 紧跟 mdat 头(8 字节)
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// moov→trak→mdia→minf→stbl→stco(offset=mdatAbs)
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stbl := box("stbl", stcoBox(mdatAbs))
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minf := box("minf", stbl)
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mdia := box("mdia", minf)
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trak := box("trak", mdia)
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moov := box("moov", trak)
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out := append([]byte(nil), ftyp...)
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out = append(out, mdat...)
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out = append(out, moov...)
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return out, mdatAbs
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}
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func TestFaststartMP4MovesMoovAndFixesOffsets(t *testing.T) {
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marker := []byte("THE-REAL-CHUNK-DATA-HERE")
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// mdat payload：前面填充 + marker，stco 指向 marker 的绝对偏移。
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pad := bytes.Repeat([]byte{0xAB}, 40)
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mdatPayload := append(append([]byte(nil), pad...), marker...)
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_, mdatAbs := buildMoovEndMP4(mdatPayload)
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markerAbs := mdatAbs + uint32(len(pad)) // marker 在原文件里的绝对偏移
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// 原 stco 指向 mdatAbs（mdat payload 头）。这里把 stco 改成指向 marker 以便断言。
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in2, _ := buildMoovEndMP4Marker(mdatPayload, markerAbs)
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// 校验前置：原文件里 markerAbs 处确实是 marker。
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if !bytes.Equal(in2[markerAbs:markerAbs+uint32(len(marker))], marker) {
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t.Fatalf("setup: 原文件 markerAbs 处非 marker")
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}
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out, changed := faststartMP4(in2)
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if !changed {
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t.Fatalf("changed = false, want true（moov 在末尾应被搬动）")
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}
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if len(out) != len(in2) {
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t.Fatalf("size 不守恒: in=%d out=%d", len(in2), len(out))
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}
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// 输出顺序：ftyp, moov, mdat。
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boxes, ok := parseTopLevelBoxes(out)
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if !ok || len(boxes) != 3 || boxes[0].typ != "ftyp" || boxes[1].typ != "moov" || boxes[2].typ != "mdat" {
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t.Fatalf("输出顶层顺序错: %+v ok=%v", boxes, ok)
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}
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// 取出输出 moov 里的 stco 偏移，应指向输出文件里仍是 marker 的位置。
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newOff := readSingleStcoOffset(t, out[boxes[1].start:boxes[1].end])
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if int(newOff)+len(marker) > len(out) {
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t.Fatalf("新偏移越界: %d", newOff)
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}
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got := out[newOff : int(newOff)+len(marker)]
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if !bytes.Equal(got, marker) {
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t.Fatalf("新 stco 偏移 %d 指向 %q, want %q（偏移修正错误）", newOff, got, marker)
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}
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// 新偏移 = 原偏移 + moovSize。
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moovSize := boxes[1].end - boxes[1].start
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if int(newOff) != int(markerAbs)+moovSize {
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t.Fatalf("新偏移 = %d, want 原 %d + moovSize %d", newOff, markerAbs, moovSize)
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}
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}
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func TestFaststartMP4NoopWhenAlreadyFaststart(t *testing.T) {
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// moov 在 mdat 前 → 已 faststart，应原样返回。
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ftyp := box("ftyp", []byte("isom\x00\x00\x02\x00"))
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stbl := box("stbl", stcoBox(100))
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moov := box("moov", box("trak", box("mdia", box("minf", stbl))))
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mdat := box("mdat", bytes.Repeat([]byte{1}, 64))
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in := append(append(append([]byte(nil), ftyp...), moov...), mdat...)
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out, changed := faststartMP4(in)
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if changed {
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t.Fatalf("已 faststart 不应改动")
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}
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if !bytes.Equal(out, in) {
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t.Fatalf("应原样返回")
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}
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}
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func TestInspectMP4LayoutDetectsMoovAtEnd(t *testing.T) {
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in, _ := buildMoovEndMP4(bytes.Repeat([]byte{0xCD}, 100))
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readAt := func(off, n int64) ([]byte, error) {
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if off+n > int64(len(in)) {
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n = int64(len(in)) - off
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}
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return in[off : off+n], nil
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}
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l, ok := inspectMP4Layout(int64(len(in)), readAt)
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if !ok {
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t.Fatalf("inspect 失败")
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}
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if !l.needsFaststart {
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t.Fatalf("moov 在末尾应 needsFaststart=true")
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}
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if !l.moovIsLast {
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t.Fatalf("moov 是最后一个 box 应 moovIsLast=true")
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}
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if l.ftypStart != 0 || l.moovEnd != int64(len(in)) {
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t.Fatalf("range 不对: %+v (len=%d)", l, len(in))
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}
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}
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func TestInspectMP4LayoutNoFaststartWhenMoovFirst(t *testing.T) {
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ftyp := box("ftyp", []byte("isom\x00\x00\x02\x00"))
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moov := box("moov", box("trak", box("mdia", box("minf", box("stbl", stcoBox(100))))))
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mdat := box("mdat", bytes.Repeat([]byte{1}, 100))
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in := append(append(append([]byte(nil), ftyp...), moov...), mdat...)
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readAt := func(off, n int64) ([]byte, error) {
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if off+n > int64(len(in)) {
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n = int64(len(in)) - off
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}
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return in[off : off+n], nil
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}
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l, ok := inspectMP4Layout(int64(len(in)), readAt)
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if !ok || l.needsFaststart {
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t.Fatalf("moov 在前应 needsFaststart=false, got ok=%v %+v", ok, l)
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}
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}
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// 流式拼接(ftyp + patched moov + 中段)必须与全量 faststartMP4 输出逐字节一致。
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func TestStreamingAssemblyMatchesFullRewrite(t *testing.T) {
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in, _ := buildMoovEndMP4(bytes.Repeat([]byte{0xEE}, 256))
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readAt := func(off, n int64) ([]byte, error) { return in[off : off+n], nil }
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l, ok := inspectMP4Layout(int64(len(in)), readAt)
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if !ok || !l.needsFaststart || !l.moovIsLast {
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t.Fatalf("setup: %+v ok=%v", l, ok)
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}
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// 流式版本：ftyp + patched moov + in[ftypEnd:moovStart]
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ftyp := append([]byte(nil), in[l.ftypStart:l.ftypEnd]...)
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moov := append([]byte(nil), in[l.moovStart:l.moovEnd]...)
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if !patchChunkOffsets(moov, l.moovEnd-l.moovStart) {
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t.Fatalf("patch 失败")
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}
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var streaming []byte
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streaming = append(streaming, ftyp...)
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streaming = append(streaming, moov...)
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streaming = append(streaming, in[l.ftypEnd:l.moovStart]...)
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full, changed := faststartMP4(in)
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if !changed {
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t.Fatalf("full 应 changed")
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}
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if !bytes.Equal(streaming, full) {
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t.Fatalf("流式拼接与全量重写不一致: streaming=%d full=%d", len(streaming), len(full))
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}
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}
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func TestFaststartMP4NoopOnNonMP4(t *testing.T) {
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for _, data := range [][]byte{
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nil,
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[]byte("not an mp4 at all"),
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{0, 0, 0, 4}, // size 太小
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} {
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if out, changed := faststartMP4(data); changed || !bytes.Equal(out, data) {
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t.Fatalf("非 MP4 应原样不动: changed=%v", changed)
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}
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}
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}
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// buildMoovEndMP4Marker 同 buildMoovEndMP4，但 stco 指向给定绝对偏移。
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func buildMoovEndMP4Marker(mdatPayload []byte, stcoOffset uint32) ([]byte, uint32) {
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ftyp := box("ftyp", []byte("isom\x00\x00\x02\x00"))
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mdat := box("mdat", mdatPayload)
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mdatAbs := uint32(len(ftyp) + 8)
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stbl := box("stbl", stcoBox(stcoOffset))
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moov := box("moov", box("trak", box("mdia", box("minf", stbl))))
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out := append([]byte(nil), ftyp...)
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out = append(out, mdat...)
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out = append(out, moov...)
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return out, mdatAbs
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}
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func readSingleStcoOffset(t *testing.T, moov []byte) uint32 {
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t.Helper()
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idx := bytes.Index(moov, []byte("stco"))
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if idx < 0 {
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t.Fatalf("moov 里找不到 stco")
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}
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// stco 头后：type(4) 已在 idx；payload 从 idx+4 起 = ver+flags(4)+count(4)+offset(4)
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off := idx + 4 + 4 + 4
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return binary.BigEndian.Uint32(moov[off : off+4])
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}
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