From c1a48408cfc3a24d1556b8b972a1fd524891bba5 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Sun, 20 Feb 2011 12:02:42 +0000
Subject: [PATCH] Cache shader source CRCs to avoid costly recompilations.

---
 src/shader.cpp | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/shader.cpp b/src/shader.cpp
index 93fc88f5..b0a8da55 100644
--- a/src/shader.cpp
+++ b/src/shader.cpp
@@ -38,20 +38,42 @@ class ShaderData
 
 private:
     GLuint prog_id, vert_id, frag_id;
+    uint32_t vert_crc, frag_crc;
+
+    /* Global shader cache */
+    static Shader *shaders[];
+    static int nshaders;
 };
 
+Shader *ShaderData::shaders[256];
+int ShaderData::nshaders = 0;
+
 /*
  * Public Shader class
  */
 
 Shader *Shader::Create(char const *vert, char const *frag)
 {
-    return new Shader(vert, frag);
+    uint32_t new_vert_crc = Hash::Crc32(vert);
+    uint32_t new_frag_crc = Hash::Crc32(frag);
+
+    for (int n = 0; n < ShaderData::nshaders; n++)
+    {
+        if (ShaderData::shaders[n]->data->vert_crc == new_vert_crc
+             && ShaderData::shaders[n]->data->frag_crc == new_frag_crc)
+            return ShaderData::shaders[n];
+    }
+
+    Shader *ret = new Shader(vert, frag);
+    ShaderData::shaders[ShaderData::nshaders] = ret;
+    ShaderData::nshaders++;
+    return ret;
 }
 
 void Shader::Destroy(Shader *shader)
 {
-    delete shader;
+    /* XXX: do nothing! the shader should remain in cache */
+    (void)shader;
 }
 
 Shader::Shader(char const *vert, char const *frag)
@@ -60,6 +82,7 @@ Shader::Shader(char const *vert, char const *frag)
     char buf[4096];
     GLsizei len;
 
+    data->vert_crc = Hash::Crc32(vert);
     data->vert_id = glCreateShader(GL_VERTEX_SHADER);
     glShaderSource(data->vert_id, 1, &vert, NULL);
     glCompileShader(data->vert_id);
@@ -68,6 +91,7 @@ Shader::Shader(char const *vert, char const *frag)
     if (len > 0)
         fprintf(stderr, "ERROR: failed to compile vertex shader: %s", buf);
 
+    data->frag_crc = Hash::Crc32(frag);
     data->frag_id = glCreateShader(GL_FRAGMENT_SHADER);
     glShaderSource(data->frag_id, 1, &frag, NULL);
     glCompileShader(data->frag_id);