SDL2源代码分析6：复制到渲染器（SDL_RenderCopy()）

骑猪看日落 2022-08-20 05:23 161阅读 0赞

=====================================================

SDL源代码分析系列文章列表：

[SDL2源代码分析1：初始化（SDL\_Init()）][SDL2_1_SDL_Init]

[SDL2源代码分析2：窗口（SDL\_Window）][SDL2_2_SDL_Window]

[SDL2源代码分析3：渲染器（SDL\_Renderer）][SDL2_3_SDL_Renderer]

[SDL2源代码分析4：纹理（SDL\_Texture）][SDL2_4_SDL_Texture]

[SDL2源代码分析5：更新纹理（SDL\_UpdateTexture()）][SDL2_5_SDL_UpdateTexture]

[SDL2源代码分析6：复制到渲染器（SDL\_RenderCopy()）][SDL2_6_SDL_RenderCopy]

[SDL2源代码分析7：显示（SDL\_RenderPresent()）][SDL2_7_SDL_RenderPresent]

[SDL2源代码分析8：视频显示总结][SDL2_8]

=====================================================

上一篇文章分析了SDL更新纹理像素数据的函数SDL\_UpdateTexture()。这篇文章继续分析SDL的源代码。本文分析SDL纹理复制到渲染目标的函数SDL\_RenderCopy()。

![20141107170527445][]

SDL播放视频的代码流程如下所示。  
初始化:

> SDL\_Init(): 初始化SDL。  
> SDL\_CreateWindow(): 创建窗口（Window）。  
> SDL\_CreateRenderer(): 基于窗口创建渲染器（Render）。  
> SDL\_CreateTexture(): 创建纹理（Texture）。

循环渲染数据:

> SDL\_UpdateTexture(): 设置纹理的数据。  
> SDL\_RenderCopy(): 纹理复制给渲染器。  
> SDL\_RenderPresent(): 显示。

上篇文章分析了该流程中的第5个函数SDL\_UpdateTexture()。本文继续分析该流程中的第6个函数SDL\_RenderCopy()。

## SDL\_RenderCopy() ##

### 函数简介 ###

SDL使用SDL\_RenderCopy()将纹理数据复制给渲染目标。SDL\_RenderCopy()的原型如下。

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1.  **int** SDLCALL SDL\_RenderCopy(SDL\_Renderer \* renderer, 
2.   SDL\_Texture \* texture, 
3.  **const** SDL\_Rect \* srcrect, 
4.  **const** SDL\_Rect \* dstrect);

参数的含义如下。  
renderer：渲染目标。  
texture：输入纹理。  
srcrect：选择输入纹理的一块矩形区域作为输入。设置为NULL的时候整个纹理作为输入。  
dstrect：选择渲染目标的一块矩形区域作为输出。设置为NULL的时候整个渲染目标作为输出。

成功的话返回0，失败的话返回-1。

### 函数调用关系图 ###

SDL\_RenderCopy()关键函数的调用关系可以用下图表示。

[![SouthEast][]][SouthEast 1]

上面的图片不太清晰，更清晰的图片上传到了相册里面：

[http://my.csdn.net/leixiaohua1020/album/detail/1793911][SouthEast 1]

把相册里面的图片保存下来就可以得到清晰的图片了。

### 源代码分析 ###

SDL\_RenderCopy()的源代码位于render\\SDL\_render.c中，如下所示。

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1.  **int** SDL\_RenderCopy(SDL\_Renderer \* renderer, SDL\_Texture \* texture, 
2.  **const** SDL\_Rect \* srcrect, **const** SDL\_Rect \* dstrect) 
3.  \{ 
4.   SDL\_Rect real\_srcrect = \{ 0, 0, 0, 0 \}; 
5.   SDL\_Rect real\_dstrect = \{ 0, 0, 0, 0 \}; 
6.   SDL\_FRect frect; 
7.  
8.  
9.   CHECK\_RENDERER\_MAGIC(renderer, -1); 
10.  CHECK\_TEXTURE\_MAGIC(texture, -1); 
11. 
12. 
13. **if** (renderer != texture->renderer) \{ 
14. **return** SDL\_SetError("Texture was not created with this renderer"); 
15.  \} 
16. 
17. 
18.  real\_srcrect.x = 0; 
19.  real\_srcrect.y = 0; 
20.  real\_srcrect.w = texture->w; 
21.  real\_srcrect.h = texture->h; 
22. **if** (srcrect) \{ 
23. **if** (!SDL\_IntersectRect(srcrect, &real\_srcrect, &real\_srcrect)) \{ 
24. **return** 0; 
25.  \} 
26.  \} 
27. 
28. 
29.  SDL\_RenderGetViewport(renderer, &real\_dstrect); 
30.  real\_dstrect.x = 0; 
31.  real\_dstrect.y = 0; 
32. **if** (dstrect) \{ 
33. **if** (!SDL\_HasIntersection(dstrect, &real\_dstrect)) \{ 
34. **return** 0; 
35.  \} 
36.  real\_dstrect = \*dstrect; 
37.  \} 
38. 
39. 
40. **if** (texture->native) \{ 
41.  texture = texture->native; 
42.  \} 
43. 
44. 
45. /\* Don't draw while we're hidden \*/
46. **if** (renderer->hidden) \{ 
47. **return** 0; 
48.  \} 
49. 
50. 
51.  frect.x = real\_dstrect.x \* renderer->scale.x; 
52.  frect.y = real\_dstrect.y \* renderer->scale.y; 
53.  frect.w = real\_dstrect.w \* renderer->scale.x; 
54.  frect.h = real\_dstrect.h \* renderer->scale.y; 
55. 
56. 
57. **return** renderer->RenderCopy(renderer, texture, &real\_srcrect, &frect); 
58. \}

从源代码中可以看出，SDL\_RenderCopy()的大致流程如下。

1.检查输入参数的合理性。  
2.调用SDL\_Render的RenderCopy ()方法复制纹理到渲染目标。 这一步是整个函数的核心。  
下面我们详细看一下几种不同的渲染器的RenderCopy()的方法。

#### 1.Direct3D ####

Direct3D 渲染器中对应RenderCopy()的函数是D3D\_RenderCopy()，它的源代码如下所示（位于render\\direct3d\\SDL\_render\_d3d.c）。

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1.  **static****int** D3D\_RenderCopy(SDL\_Renderer \* renderer, SDL\_Texture \* texture, 
2.  **const** SDL\_Rect \* srcrect, **const** SDL\_FRect \* dstrect) 
3.  \{ 
4.   D3D\_RenderData \*data = (D3D\_RenderData \*) renderer->driverdata; 
5.   D3D\_TextureData \*texturedata; 
6.   LPDIRECT3DPIXELSHADER9 shader = NULL; 
7.  **float** minx, miny, maxx, maxy; 
8.  **float** minu, maxu, minv, maxv; 
9.  **DWORD** color; 
10.  Vertex vertices\[4\]; 
11. **HRESULT** result; 
12. 
13. 
14. **if** (D3D\_ActivateRenderer(renderer) < 0) \{ 
15. **return** \-1; 
16.  \} 
17. 
18. 
19.  texturedata = (D3D\_TextureData \*)texture->driverdata; 
20. **if** (!texturedata) \{ 
21.  SDL\_SetError("Texture is not currently available"); 
22. **return** \-1; 
23.  \} 
24. 
25. 
26.  minx = dstrect->x - 0.5f; 
27.  miny = dstrect->y - 0.5f; 
28.  maxx = dstrect->x + dstrect->w - 0.5f; 
29.  maxy = dstrect->y + dstrect->h - 0.5f; 
30. 
31. 
32.  minu = (**float**) srcrect->x / texture->w; 
33.  maxu = (**float**) (srcrect->x + srcrect->w) / texture->w; 
34.  minv = (**float**) srcrect->y / texture->h; 
35.  maxv = (**float**) (srcrect->y + srcrect->h) / texture->h; 
36. 
37. 
38.  color = D3DCOLOR\_ARGB(texture->a, texture->r, texture->g, texture->b); 
39. 
40. 
41.  vertices\[0\].x = minx; 
42.  vertices\[0\].y = miny; 
43.  vertices\[0\].z = 0.0f; 
44.  vertices\[0\].color = color; 
45.  vertices\[0\].u = minu; 
46.  vertices\[0\].v = minv; 
47. 
48. 
49.  vertices\[1\].x = maxx; 
50.  vertices\[1\].y = miny; 
51.  vertices\[1\].z = 0.0f; 
52.  vertices\[1\].color = color; 
53.  vertices\[1\].u = maxu; 
54.  vertices\[1\].v = minv; 
55. 
56. 
57.  vertices\[2\].x = maxx; 
58.  vertices\[2\].y = maxy; 
59.  vertices\[2\].z = 0.0f; 
60.  vertices\[2\].color = color; 
61.  vertices\[2\].u = maxu; 
62.  vertices\[2\].v = maxv; 
63. 
64. 
65.  vertices\[3\].x = minx; 
66.  vertices\[3\].y = maxy; 
67.  vertices\[3\].z = 0.0f; 
68.  vertices\[3\].color = color; 
69.  vertices\[3\].u = minu; 
70.  vertices\[3\].v = maxv; 
71. 
72. 
73.  D3D\_SetBlendMode(data, texture->blendMode); 
74. 
75. 
76.  D3D\_UpdateTextureScaleMode(data, texturedata, 0); 
77. 
78. 
79.  result = 
80.  IDirect3DDevice9\_SetTexture(data->device, 0, (IDirect3DBaseTexture9 \*) 
81.  texturedata->texture); 
82. **if** (FAILED(result)) \{ 
83. **return** D3D\_SetError("SetTexture()", result); 
84.  \} 
85. 
86. 
87. **if** (texturedata->yuv) \{ 
88.  shader = data->ps\_yuv; 
89. 
90. 
91.  D3D\_UpdateTextureScaleMode(data, texturedata, 1); 
92.  D3D\_UpdateTextureScaleMode(data, texturedata, 2); 
93. 
94. 
95.  result = 
96.  IDirect3DDevice9\_SetTexture(data->device, 1, (IDirect3DBaseTexture9 \*) 
97.  texturedata->utexture); 
98. **if** (FAILED(result)) \{ 
99. **return** D3D\_SetError("SetTexture()", result); 
100.  \} 
101. 
102. 
103.  result = 
104.  IDirect3DDevice9\_SetTexture(data->device, 2, (IDirect3DBaseTexture9 \*) 
105.  texturedata->vtexture); 
106. **if** (FAILED(result)) \{ 
107. **return** D3D\_SetError("SetTexture()", result); 
108.  \} 
109.  \} 
110. 
111. 
112. **if** (shader) \{ 
113.  result = IDirect3DDevice9\_SetPixelShader(data->device, shader); 
114. **if** (FAILED(result)) \{ 
115. **return** D3D\_SetError("SetShader()", result); 
116.  \} 
117.  \} 
118.  result = 
119.  IDirect3DDevice9\_DrawPrimitiveUP(data->device, D3DPT\_TRIANGLEFAN, 2, 
120.  vertices, **sizeof**(\*vertices)); 
121. **if** (FAILED(result)) \{ 
122. **return** D3D\_SetError("DrawPrimitiveUP()", result); 
123.  \} 
124. **if** (shader) \{ 
125.  result = IDirect3DDevice9\_SetPixelShader(data->device, NULL); 
126. **if** (FAILED(result)) \{ 
127. **return** D3D\_SetError("SetShader()", result); 
128.  \} 
129.  \} 
130. **return** 0; 
131. \}

从代码中可以看出，D3D\_RenderCopy()函数按照执行的顺序调用了如下函数：

> D3D\_ActivateRenderer()：激活渲染器。其内部使用Direct3D的API函数IDirect3DDevice9\_BeginScene()开始一个D3D的场景。  
> D3D\_SetBlendMode()：设置渲染器状态。其内部使用Direct3D的API函数IDirect3DDevice9\_SetRenderState()设置渲染器的状态。  
> D3D\_UpdateTextureScaleMode()：设置纹理采样方式。其内部调用使用Direct3D的API函数IDirect3DDevice9\_SetSamplerState()设置D3D的纹理采样方式。  
> IDirect3DDevice9\_SetTexture()：Direct3D的API，用于设置当前启用的纹理。  
> IDirect3DDevice9\_SetPixelShader()：Direct3D的API，用于设置使用的像素着色器。
> 
> IDirect3DDevice9\_DrawPrimitiveUP()：Direct3D的API，用于渲染。

上述几个函数中，前3个函数是SDL中的函数，后3个函数是Direct3D的API。在此附上前三个函数的代码。

**D3D\_ActivateRenderer()：激活渲染器。**

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1.  **static****int** D3D\_ActivateRenderer(SDL\_Renderer \* renderer) 
2.  \{ 
3.   D3D\_RenderData \*data = (D3D\_RenderData \*) renderer->driverdata; 
4.  **HRESULT** result; 
5.  
6.  
7.  **if** (data->updateSize) \{ 
8.   SDL\_Window \*window = renderer->window; 
9.  **int** w, h; 
10. 
11. 
12.  SDL\_GetWindowSize(window, &w, &h); 
13.  data->pparams.BackBufferWidth = w; 
14.  data->pparams.BackBufferHeight = h; 
15. **if** (SDL\_GetWindowFlags(window) & SDL\_WINDOW\_FULLSCREEN) \{ 
16.  data->pparams.BackBufferFormat = 
17.  PixelFormatToD3DFMT(SDL\_GetWindowPixelFormat(window)); 
18.  \} **else** \{ 
19.  data->pparams.BackBufferFormat = D3DFMT\_UNKNOWN; 
20.  \} 
21. **if** (D3D\_Reset(renderer) < 0) \{ 
22. **return** \-1; 
23.  \} 
24. 
25. 
26.  data->updateSize = SDL\_FALSE; 
27.  \} 
28. **if** (data->beginScene) \{ 
29.  result = IDirect3DDevice9\_BeginScene(data->device); 
30. **if** (result == D3DERR\_DEVICELOST) \{ 
31. **if** (D3D\_Reset(renderer) < 0) \{ 
32. **return** \-1; 
33.  \} 
34.  result = IDirect3DDevice9\_BeginScene(data->device); 
35.  \} 
36. **if** (FAILED(result)) \{ 
37. **return** D3D\_SetError("BeginScene()", result); 
38.  \} 
39.  data->beginScene = SDL\_FALSE; 
40.  \} 
41. **return** 0; 
42. \}

**D3D\_SetBlendMode()：设置渲染器状态。**

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1.  **static****void** D3D\_SetBlendMode(D3D\_RenderData \* data, **int** blendMode) 
2.  \{ 
3.  **switch** (blendMode) \{ 
4.  **case** SDL\_BLENDMODE\_NONE: 
5.   IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_ALPHABLENDENABLE, 
6.   FALSE); 
7.  **break**; 
8.  **case** SDL\_BLENDMODE\_BLEND: 
9.   IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_ALPHABLENDENABLE, 
10.  TRUE); 
11.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_SRCBLEND, 
12.  D3DBLEND\_SRCALPHA); 
13.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_DESTBLEND, 
14.  D3DBLEND\_INVSRCALPHA); 
15. **if** (data->enableSeparateAlphaBlend) \{ 
16.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_SRCBLENDALPHA, 
17.  D3DBLEND\_ONE); 
18.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_DESTBLENDALPHA, 
19.  D3DBLEND\_INVSRCALPHA); 
20.  \} 
21. **break**; 
22. **case** SDL\_BLENDMODE\_ADD: 
23.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_ALPHABLENDENABLE, 
24.  TRUE); 
25.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_SRCBLEND, 
26.  D3DBLEND\_SRCALPHA); 
27.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_DESTBLEND, 
28.  D3DBLEND\_ONE); 
29. **if** (data->enableSeparateAlphaBlend) \{ 
30.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_SRCBLENDALPHA, 
31.  D3DBLEND\_ZERO); 
32.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_DESTBLENDALPHA, 
33.  D3DBLEND\_ONE); 
34.  \} 
35. **break**; 
36. **case** SDL\_BLENDMODE\_MOD: 
37.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_ALPHABLENDENABLE, 
38.  TRUE); 
39.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_SRCBLEND, 
40.  D3DBLEND\_ZERO); 
41.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_DESTBLEND, 
42.  D3DBLEND\_SRCCOLOR); 
43. **if** (data->enableSeparateAlphaBlend) \{ 
44.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_SRCBLENDALPHA, 
45.  D3DBLEND\_ZERO); 
46.  IDirect3DDevice9\_SetRenderState(data->device, D3DRS\_DESTBLENDALPHA, 
47.  D3DBLEND\_ONE); 
48.  \} 
49. **break**; 
50.  \} 
51. \}

**D3D\_UpdateTextureScaleMode()：设置纹理采样方式。**

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1.  **static****void** D3D\_UpdateTextureScaleMode(D3D\_RenderData \*data, D3D\_TextureData \*texturedata, unsigned index) 
2.  \{ 
3.  **if** (texturedata->scaleMode != data->scaleMode\[index\]) \{ 
4.   IDirect3DDevice9\_SetSamplerState(data->device, index, D3DSAMP\_MINFILTER, 
5.   texturedata->scaleMode); 
6.   IDirect3DDevice9\_SetSamplerState(data->device, index, D3DSAMP\_MAGFILTER, 
7.   texturedata->scaleMode); 
8.   data->scaleMode\[index\] = texturedata->scaleMode; 
9.   \} 
10. \}

#### 2.OpenGL ####

OpenGL渲染器中对应RenderCopy()的函数是GL\_RenderCopy()，它的源代码如下所示（位于render\\opengl\\SDL\_render\_gl.c）。

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1.  **static****int** GL\_RenderCopy(SDL\_Renderer \* renderer, SDL\_Texture \* texture, 
2.  **const** SDL\_Rect \* srcrect, **const** SDL\_FRect \* dstrect) 
3.  \{ 
4.   GL\_RenderData \*data = (GL\_RenderData \*) renderer->driverdata; 
5.   GL\_TextureData \*texturedata = (GL\_TextureData \*) texture->driverdata; 
6.   GLfloat minx, miny, maxx, maxy; 
7.   GLfloat minu, maxu, minv, maxv; 
8.  
9.  
10.  GL\_ActivateRenderer(renderer); 
11. 
12. 
13.  data->glEnable(texturedata->type); 
14. **if** (texturedata->yuv) \{ 
15.  data->glActiveTextureARB(GL\_TEXTURE2\_ARB); 
16.  data->glBindTexture(texturedata->type, texturedata->vtexture); 
17. 
18. 
19.  data->glActiveTextureARB(GL\_TEXTURE1\_ARB); 
20.  data->glBindTexture(texturedata->type, texturedata->utexture); 
21. 
22. 
23.  data->glActiveTextureARB(GL\_TEXTURE0\_ARB); 
24.  \} 
25.  data->glBindTexture(texturedata->type, texturedata->texture); 
26. 
27. 
28. **if** (texture->modMode) \{ 
29.  GL\_SetColor(data, texture->r, texture->g, texture->b, texture->a); 
30.  \} **else** \{ 
31.  GL\_SetColor(data, 255, 255, 255, 255); 
32.  \} 
33. 
34. 
35.  GL\_SetBlendMode(data, texture->blendMode); 
36. 
37. 
38. **if** (texturedata->yuv) \{ 
39.  GL\_SetShader(data, SHADER\_YV12); 
40.  \} **else** \{ 
41.  GL\_SetShader(data, SHADER\_RGB); 
42.  \} 
43. 
44. 
45.  minx = dstrect->x; 
46.  miny = dstrect->y; 
47.  maxx = dstrect->x + dstrect->w; 
48.  maxy = dstrect->y + dstrect->h; 
49. 
50. 
51.  minu = (GLfloat) srcrect->x / texture->w; 
52.  minu \*= texturedata->texw; 
53.  maxu = (GLfloat) (srcrect->x + srcrect->w) / texture->w; 
54.  maxu \*= texturedata->texw; 
55.  minv = (GLfloat) srcrect->y / texture->h; 
56.  minv \*= texturedata->texh; 
57.  maxv = (GLfloat) (srcrect->y + srcrect->h) / texture->h; 
58.  maxv \*= texturedata->texh; 
59. 
60. 
61.  data->glBegin(GL\_TRIANGLE\_STRIP); 
62.  data->glTexCoord2f(minu, minv); 
63.  data->glVertex2f(minx, miny); 
64.  data->glTexCoord2f(maxu, minv); 
65.  data->glVertex2f(maxx, miny); 
66.  data->glTexCoord2f(minu, maxv); 
67.  data->glVertex2f(minx, maxy); 
68.  data->glTexCoord2f(maxu, maxv); 
69.  data->glVertex2f(maxx, maxy); 
70.  data->glEnd(); 
71. 
72. 
73.  data->glDisable(texturedata->type); 
74. 
75. 
76. **return** GL\_CheckError("", renderer); 
77. \}

从代码中可以看出，GL\_RenderCopy()函数调用了OpenGL的API函数glActiveTexture()，glBindTexture()创建了一个纹理。并且使用GL\_SetBlendMode()，GL\_SetShader()设置了有关的一些参数。

有一点需要注意，在OpenGL渲染器中，如果输入像素格式是YUV，就会使用3个纹理。

#### 3.Software ####

Software渲染器中对应RenderCopy()的函数是SW\_RenderCopy()，它的源代码如下所示（位于render\\software\\SDL\_render\_sw.c）。

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1.  **static****int** SW\_RenderCopy(SDL\_Renderer \* renderer, SDL\_Texture \* texture, 
2.  **const** SDL\_Rect \* srcrect, **const** SDL\_FRect \* dstrect) 
3.  \{ 
4.   SDL\_Surface \*surface = SW\_ActivateRenderer(renderer); 
5.   SDL\_Surface \*src = (SDL\_Surface \*) texture->driverdata; 
6.   SDL\_Rect final\_rect; 
7.  
8.  
9.  **if** (!surface) \{ 
10. **return** \-1; 
11.  \} 
12. 
13. 
14. **if** (renderer->viewport.x || renderer->viewport.y) \{ 
15.  final\_rect.x = (**int**)(renderer->viewport.x + dstrect->x); 
16.  final\_rect.y = (**int**)(renderer->viewport.y + dstrect->y); 
17.  \} **else** \{ 
18.  final\_rect.x = (**int**)dstrect->x; 
19.  final\_rect.y = (**int**)dstrect->y; 
20.  \} 
21.  final\_rect.w = (**int**)dstrect->w; 
22.  final\_rect.h = (**int**)dstrect->h; 
23. 
24. 
25. **if** ( srcrect->w == final\_rect.w && srcrect->h == final\_rect.h ) \{ 
26. **return** SDL\_BlitSurface(src, srcrect, surface, &final\_rect); 
27.  \} **else** \{ 
28. **return** SDL\_BlitScaled(src, srcrect, surface, &final\_rect); 
29.  \} 
30. \}

该函数的源代码还没有详细分析。

[SDL2_1_SDL_Init]: http://blog.csdn.net/leixiaohua1020/article/details/40680907
[SDL2_2_SDL_Window]: http://blog.csdn.net/leixiaohua1020/article/details/40701203
[SDL2_3_SDL_Renderer]: http://blog.csdn.net/leixiaohua1020/article/details/40723085
[SDL2_4_SDL_Texture]: http://blog.csdn.net/leixiaohua1020/article/details/40743061
[SDL2_5_SDL_UpdateTexture]: http://blog.csdn.net/leixiaohua1020/article/details/40876089
[SDL2_6_SDL_RenderCopy]: http://blog.csdn.net/leixiaohua1020/article/details/40895593
[SDL2_7_SDL_RenderPresent]: http://blog.csdn.net/leixiaohua1020/article/details/40895797
[SDL2_8]: http://blog.csdn.net/leixiaohua1020/article/details/41207787
[20141107170527445]: /images/20220731/6116ae5da0154895bf64107936d771a5.png
[view plain]: http://blog.csdn.net/leixiaohua1020/article/details/40895593#
[CODE]: https://code.csdn.net/assets/CODE_ico.png
[CODE_CODE]: https://code.csdn.net/snippets/512083
[ico_fork.svg]: https://code.csdn.net/assets/ico_fork.svg
[ico_fork.svg 1]: https://code.csdn.net/snippets/512083/fork
[SouthEast]: /images/20220731/6a16fa402c3b4a94a18ed47b212018e9.png
[SouthEast 1]: http://my.csdn.net/leixiaohua1020/album/detail/1793911