Refactored entry point validation functions into their own files.

TRAC #23629

Signed-off-by: Nicolas Capens
Signed-off-by: Shannon Woods
Author: Geoff Lang
diff --git a/src/libGLESv2/validationES2.cpp b/src/libGLESv2/validationES2.cpp
new file mode 100644
index 0000000..9f4284a
--- /dev/null
+++ b/src/libGLESv2/validationES2.cpp
@@ -0,0 +1,1009 @@
+#include "precompiled.h"
+//
+// Copyright (c) 2013 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+
+// validationES2.cpp: Validation functions for OpenGL ES 2.0 entry point parameters
+
+#include "libGLESv2/validationES2.h"
+#include "libGLESv2/Context.h"
+#include "libGLESv2/Texture.h"
+#include "libGLESv2/Framebuffer.h"
+#include "libGLESv2/Renderbuffer.h"
+#include "libGLESv2/formatutils.h"
+#include "libGLESv2/main.h"
+
+#include "common/mathutil.h"
+#include "common/utilities.h"
+
+namespace gl
+{
+
+static bool validImageSize(const gl::Context *context, GLint level, GLsizei width, GLsizei height, GLsizei depth)
+{
+    if (level < 0 || width < 0 || height < 0 || depth < 0)
+    {
+        return false;
+    }
+
+    if (context->supportsNonPower2Texture())
+    {
+        return true;
+    }
+
+    if (level == 0)
+    {
+        return true;
+    }
+
+    if (gl::isPow2(width) && gl::isPow2(height) && gl::isPow2(depth))
+    {
+        return true;
+    }
+
+    return false;
+}
+
+static bool validCompressedImageSize(GLsizei width, GLsizei height)
+{
+    if (width != 1 && width != 2 && width % 4 != 0)
+    {
+        return false;
+    }
+
+    if (height != 1 && height != 2 && height % 4 != 0)
+    {
+        return false;
+    }
+
+    return true;
+}
+
+static bool validateSubImageParams2D(bool compressed, GLsizei width, GLsizei height,
+                                     GLint xoffset, GLint yoffset, GLint level, GLenum format, GLenum type,
+                                     gl::Texture2D *texture)
+{
+    if (!texture)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (compressed != texture->isCompressed(level))
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (format != GL_NONE)
+    {
+        GLenum internalformat = gl::GetSizedInternalFormat(format, type, 2);
+        if (internalformat != texture->getInternalFormat(level))
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+    }
+
+    if (compressed)
+    {
+        if ((width % 4 != 0 && width != texture->getWidth(0)) ||
+            (height % 4 != 0 && height != texture->getHeight(0)))
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+    }
+
+    if (xoffset + width > texture->getWidth(level) ||
+        yoffset + height > texture->getHeight(level))
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    return true;
+}
+
+static bool validateSubImageParamsCube(bool compressed, GLsizei width, GLsizei height,
+                                       GLint xoffset, GLint yoffset, GLenum target, GLint level, GLenum format, GLenum type,
+                                       gl::TextureCubeMap *texture)
+{
+    if (!texture)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (compressed != texture->isCompressed(target, level))
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (format != GL_NONE)
+    {
+        GLenum internalformat = gl::GetSizedInternalFormat(format, type, 2);
+        if (internalformat != texture->getInternalFormat(target, level))
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+    }
+
+    if (compressed)
+    {
+        if ((width % 4 != 0 && width != texture->getWidth(target, 0)) ||
+            (height % 4 != 0 && height != texture->getHeight(target, 0)))
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+    }
+
+    if (xoffset + width > texture->getWidth(target, level) ||
+        yoffset + height > texture->getHeight(target, level))
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    return true;
+}
+
+bool validateES2TexImageParameters(gl::Context *context, GLenum target, GLint level, GLint internalformat, bool isCompressed, bool isSubImage,
+                                   GLint xoffset, GLint yoffset, GLsizei width, GLsizei height,
+                                   GLint border, GLenum format, GLenum type, const GLvoid *pixels)
+{
+    if (!validImageSize(context, level, width, height, 1))
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    if (isCompressed && !validCompressedImageSize(width, height))
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (level < 0 || xoffset < 0 ||
+        std::numeric_limits<GLsizei>::max() - xoffset < width ||
+        std::numeric_limits<GLsizei>::max() - yoffset < height)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    if (!isSubImage && !isCompressed && internalformat != GLint(format))
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    gl::Texture *texture = NULL;
+    bool textureCompressed = false;
+    GLenum textureInternalFormat = GL_NONE;
+    GLint textureLevelWidth = 0;
+    GLint textureLevelHeight = 0;
+    switch (target)
+    {
+      case GL_TEXTURE_2D:
+        {
+            if (width > (context->getMaximum2DTextureDimension() >> level) ||
+                height > (context->getMaximum2DTextureDimension() >> level))
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+
+            gl::Texture2D *tex2d = context->getTexture2D();
+            if (tex2d)
+            {
+                textureCompressed = tex2d->isCompressed(level);
+                textureInternalFormat = tex2d->getInternalFormat(level);
+                textureLevelWidth = tex2d->getWidth(level);
+                textureLevelHeight = tex2d->getHeight(level);
+                texture = tex2d;
+            }
+
+            if (isSubImage && !validateSubImageParams2D(isCompressed, width, height, xoffset, yoffset,
+                                                        level, format, type, tex2d))
+            {
+                return false;
+            }
+
+            texture = tex2d;
+        }
+        break;
+
+      case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
+      case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
+      case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
+      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
+      case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
+      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
+        {
+            if (!isSubImage && width != height)
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+
+            if (width > (context->getMaximumCubeTextureDimension() >> level) ||
+                height > (context->getMaximumCubeTextureDimension() >> level))
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+
+            gl::TextureCubeMap *texCube = context->getTextureCubeMap();
+            if (texCube)
+            {
+                textureCompressed = texCube->isCompressed(target, level);
+                textureInternalFormat = texCube->getInternalFormat(target, level);
+                textureLevelWidth = texCube->getWidth(target, level);
+                textureLevelHeight = texCube->getHeight(target, level);
+                texture = texCube;
+            }
+
+            if (isSubImage && !validateSubImageParamsCube(isCompressed, width, height, xoffset, yoffset,
+                                                          target, level, format, type, texCube))
+            {
+                return false;
+            }
+        }
+        break;
+
+      default:
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    if (!texture)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (!isSubImage && texture->isImmutable())
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    // Verify zero border
+    if (border != 0)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    // Verify texture is not requesting more mip levels than are available.
+    if (level > context->getMaximumTextureLevel())
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    GLenum actualInternalFormat = isSubImage ? textureInternalFormat : internalformat;
+    if (isCompressed)
+    {
+        switch (actualInternalFormat)
+        {
+          case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+          case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+            if (!context->supportsDXT1Textures())
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
+            if (!context->supportsDXT3Textures())
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
+            if (!context->supportsDXT5Textures())
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          default:
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+    }
+    else
+    {
+        // validate <type> by itself (used as secondary key below)
+        switch (type)
+        {
+          case GL_UNSIGNED_BYTE:
+          case GL_UNSIGNED_SHORT_5_6_5:
+          case GL_UNSIGNED_SHORT_4_4_4_4:
+          case GL_UNSIGNED_SHORT_5_5_5_1:
+          case GL_UNSIGNED_SHORT:
+          case GL_UNSIGNED_INT:
+          case GL_UNSIGNED_INT_24_8_OES:
+          case GL_HALF_FLOAT_OES:
+          case GL_FLOAT:
+            break;
+          default:
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+
+        // validate <format> + <type> combinations
+        // - invalid <format> -> sets INVALID_ENUM
+        // - invalid <format>+<type> combination -> sets INVALID_OPERATION
+        switch (format)
+        {
+          case GL_ALPHA:
+          case GL_LUMINANCE:
+          case GL_LUMINANCE_ALPHA:
+            switch (type)
+            {
+              case GL_UNSIGNED_BYTE:
+              case GL_FLOAT:
+              case GL_HALF_FLOAT_OES:
+                break;
+            default:
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_RGB:
+            switch (type)
+            {
+              case GL_UNSIGNED_BYTE:
+              case GL_UNSIGNED_SHORT_5_6_5:
+              case GL_FLOAT:
+              case GL_HALF_FLOAT_OES:
+                break;
+              default:
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_RGBA:
+            switch (type)
+            {
+              case GL_UNSIGNED_BYTE:
+              case GL_UNSIGNED_SHORT_4_4_4_4:
+              case GL_UNSIGNED_SHORT_5_5_5_1:
+              case GL_FLOAT:
+              case GL_HALF_FLOAT_OES:
+                break;
+              default:
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_BGRA_EXT:
+            switch (type)
+            {
+              case GL_UNSIGNED_BYTE:
+                break;
+              default:
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:  // error cases for compressed textures are handled below
+          case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+          case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
+          case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
+            break;
+          case GL_DEPTH_COMPONENT:
+            switch (type)
+            {
+              case GL_UNSIGNED_SHORT:
+              case GL_UNSIGNED_INT:
+                break;
+              default:
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_DEPTH_STENCIL_OES:
+            switch (type)
+            {
+              case GL_UNSIGNED_INT_24_8_OES:
+                break;
+              default:
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          default:
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+
+        switch (format)
+        {
+          case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+          case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+            if (context->supportsDXT1Textures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
+            if (context->supportsDXT3Textures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
+            if (context->supportsDXT5Textures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_DEPTH_COMPONENT:
+          case GL_DEPTH_STENCIL_OES:
+            if (!context->supportsDepthTextures())
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+            if (target != GL_TEXTURE_2D)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            // OES_depth_texture supports loading depth data and multiple levels,
+            // but ANGLE_depth_texture does not
+            if (pixels != NULL || level != 0)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          default:
+            break;
+        }
+
+        if (type == GL_FLOAT)
+        {
+            if (!context->supportsFloat32Textures())
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+        }
+        else if (type == GL_HALF_FLOAT_OES)
+        {
+            if (!context->supportsFloat16Textures())
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+        }
+    }
+
+    return true;
+}
+
+
+
+bool validateES2CopyTexImageParameters(gl::Context* context, GLenum target, GLint level, GLenum internalformat, bool isSubImage,
+                                       GLint xoffset, GLint yoffset, GLint x, GLint y, GLsizei width, GLsizei height,
+                                       GLint border)
+{
+    if (!gl::IsInternalTextureTarget(target, context->getClientVersion()))
+    {
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    if (level < 0 || xoffset < 0 || yoffset < 0 || width < 0 || height < 0)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    if (std::numeric_limits<GLsizei>::max() - xoffset < width || std::numeric_limits<GLsizei>::max() - yoffset < height)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    if (width == 0 || height == 0)
+    {
+        return false;
+    }
+
+    // Verify zero border
+    if (border != 0)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    // Validate dimensions based on Context limits and validate the texture
+    if (level > context->getMaximumTextureLevel())
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    gl::Framebuffer *framebuffer = context->getReadFramebuffer();
+
+    if (framebuffer->completeness() != GL_FRAMEBUFFER_COMPLETE)
+    {
+        return gl::error(GL_INVALID_FRAMEBUFFER_OPERATION, false);
+    }
+
+    if (context->getReadFramebufferHandle() != 0 && framebuffer->getSamples() != 0)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    GLenum colorbufferFormat = framebuffer->getReadColorbuffer()->getInternalFormat();
+    gl::Texture *texture = NULL;
+    GLenum textureFormat = GL_RGBA;
+
+    switch (target)
+    {
+      case GL_TEXTURE_2D:
+        {
+            if (width > (context->getMaximum2DTextureDimension() >> level) ||
+                height > (context->getMaximum2DTextureDimension() >> level))
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+
+            gl::Texture2D *tex2d = context->getTexture2D();
+            if (tex2d)
+            {
+                if (isSubImage && !validateSubImageParams2D(false, width, height, xoffset, yoffset, level, GL_NONE, GL_NONE, tex2d))
+                {
+                    return false; // error already registered by validateSubImageParams
+                }
+                texture = tex2d;
+                textureFormat = gl::GetFormat(tex2d->getInternalFormat(level), context->getClientVersion());
+            }
+        }
+        break;
+
+      case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
+      case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
+      case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
+      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
+      case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
+      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
+        {
+            if (!isSubImage && width != height)
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+
+            if (width > (context->getMaximumCubeTextureDimension() >> level) ||
+                height > (context->getMaximumCubeTextureDimension() >> level))
+            {
+                return gl::error(GL_INVALID_VALUE, false);
+            }
+
+            gl::TextureCubeMap *texcube = context->getTextureCubeMap();
+            if (texcube)
+            {
+                if (isSubImage && !validateSubImageParamsCube(false, width, height, xoffset, yoffset, target, level, GL_NONE, GL_NONE, texcube))
+                {
+                    return false; // error already registered by validateSubImageParams
+                }
+                texture = texcube;
+                textureFormat = gl::GetFormat(texcube->getInternalFormat(target, level), context->getClientVersion());
+            }
+        }
+        break;
+
+      default:
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    if (!texture)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (texture->isImmutable() && !isSubImage)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+
+    // [OpenGL ES 2.0.24] table 3.9
+    if (isSubImage)
+    {
+        switch (textureFormat)
+        {
+          case GL_ALPHA:
+            if (colorbufferFormat != GL_ALPHA8_EXT &&
+                colorbufferFormat != GL_RGBA4 &&
+                colorbufferFormat != GL_RGB5_A1 &&
+                colorbufferFormat != GL_RGBA8_OES)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_LUMINANCE:
+          case GL_RGB:
+            if (colorbufferFormat != GL_RGB565 &&
+                colorbufferFormat != GL_RGB8_OES &&
+                colorbufferFormat != GL_RGBA4 &&
+                colorbufferFormat != GL_RGB5_A1 &&
+                colorbufferFormat != GL_RGBA8_OES)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_LUMINANCE_ALPHA:
+          case GL_RGBA:
+            if (colorbufferFormat != GL_RGBA4 &&
+                colorbufferFormat != GL_RGB5_A1 &&
+                colorbufferFormat != GL_RGBA8_OES)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+          case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+          case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
+          case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
+            return gl::error(GL_INVALID_OPERATION, false);
+          case GL_DEPTH_COMPONENT:
+          case GL_DEPTH_STENCIL_OES:
+            return gl::error(GL_INVALID_OPERATION, false);
+          default:
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+    }
+    else
+    {
+        switch (internalformat)
+        {
+          case GL_ALPHA:
+            if (colorbufferFormat != GL_ALPHA8_EXT &&
+                colorbufferFormat != GL_RGBA4 &&
+                colorbufferFormat != GL_RGB5_A1 &&
+                colorbufferFormat != GL_BGRA8_EXT &&
+                colorbufferFormat != GL_RGBA8_OES)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_LUMINANCE:
+          case GL_RGB:
+            if (colorbufferFormat != GL_RGB565 &&
+                colorbufferFormat != GL_RGB8_OES &&
+                colorbufferFormat != GL_RGBA4 &&
+                colorbufferFormat != GL_RGB5_A1 &&
+                colorbufferFormat != GL_BGRA8_EXT &&
+                colorbufferFormat != GL_RGBA8_OES)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_LUMINANCE_ALPHA:
+          case GL_RGBA:
+            if (colorbufferFormat != GL_RGBA4 &&
+                colorbufferFormat != GL_RGB5_A1 &&
+                colorbufferFormat != GL_BGRA8_EXT &&
+                colorbufferFormat != GL_RGBA8_OES)
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            break;
+          case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+          case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+            if (context->supportsDXT1Textures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
+            if (context->supportsDXT3Textures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
+            if (context->supportsDXT5Textures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+            break;
+          case GL_DEPTH_COMPONENT:
+          case GL_DEPTH_COMPONENT16:
+          case GL_DEPTH_COMPONENT32_OES:
+          case GL_DEPTH_STENCIL_OES:
+          case GL_DEPTH24_STENCIL8_OES:
+            if (context->supportsDepthTextures())
+            {
+                return gl::error(GL_INVALID_OPERATION, false);
+            }
+            else
+            {
+                return gl::error(GL_INVALID_ENUM, false);
+            }
+          default:
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+    }
+
+    return true;
+}
+
+bool validateES2TexStorageParameters(gl::Context *context, GLenum target, GLsizei levels, GLenum internalformat,
+                                     GLsizei width, GLsizei height)
+{
+    if (target != GL_TEXTURE_2D && target != GL_TEXTURE_CUBE_MAP)
+    {
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    if (width < 1 || height < 1 || levels < 1)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    if (target == GL_TEXTURE_CUBE_MAP && width != height)
+    {
+        return gl::error(GL_INVALID_VALUE, false);
+    }
+
+    if (levels != 1 && levels != gl::log2(std::max(width, height)) + 1)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    GLenum format = gl::GetFormat(internalformat, context->getClientVersion());
+    GLenum type = gl::GetType(internalformat, context->getClientVersion());
+
+    if (format == GL_NONE || type == GL_NONE)
+    {
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    switch (target)
+    {
+      case GL_TEXTURE_2D:
+        if (width > context->getMaximum2DTextureDimension() ||
+            height > context->getMaximum2DTextureDimension())
+        {
+            return gl::error(GL_INVALID_VALUE, false);
+        }
+        break;
+      case GL_TEXTURE_CUBE_MAP:
+        if (width > context->getMaximumCubeTextureDimension() ||
+            height > context->getMaximumCubeTextureDimension())
+        {
+            return gl::error(GL_INVALID_VALUE, false);
+        }
+        break;
+      default:
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    if (levels != 1 && !context->supportsNonPower2Texture())
+    {
+        if (!gl::isPow2(width) || !gl::isPow2(height))
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+    }
+
+    switch (internalformat)
+    {
+      case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+      case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+        if (!context->supportsDXT1Textures())
+        {
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+        break;
+      case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
+        if (!context->supportsDXT3Textures())
+        {
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+        break;
+      case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
+        if (!context->supportsDXT5Textures())
+        {
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+        break;
+      case GL_RGBA32F_EXT:
+      case GL_RGB32F_EXT:
+      case GL_ALPHA32F_EXT:
+      case GL_LUMINANCE32F_EXT:
+      case GL_LUMINANCE_ALPHA32F_EXT:
+        if (!context->supportsFloat32Textures())
+        {
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+        break;
+      case GL_RGBA16F_EXT:
+      case GL_RGB16F_EXT:
+      case GL_ALPHA16F_EXT:
+      case GL_LUMINANCE16F_EXT:
+      case GL_LUMINANCE_ALPHA16F_EXT:
+        if (!context->supportsFloat16Textures())
+        {
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+        break;
+      case GL_DEPTH_COMPONENT16:
+      case GL_DEPTH_COMPONENT32_OES:
+      case GL_DEPTH24_STENCIL8_OES:
+        if (!context->supportsDepthTextures())
+        {
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+        if (target != GL_TEXTURE_2D)
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+        // ANGLE_depth_texture only supports 1-level textures
+        if (levels != 1)
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+        break;
+      default:
+        break;
+    }
+
+    gl::Texture *texture = NULL;
+    switch(target)
+    {
+      case GL_TEXTURE_2D:
+        texture = context->getTexture2D();
+        break;
+      case GL_TEXTURE_CUBE_MAP:
+        texture = context->getTextureCubeMap();
+        break;
+      default:
+        UNREACHABLE();
+    }
+
+    if (!texture || texture->id() == 0)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    if (texture->isImmutable())
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    return true;
+}
+
+bool validateES2FramebufferTextureParameters(gl::Context *context, GLenum target, GLenum attachment,
+                                             GLenum textarget, GLuint texture, GLint level)
+{
+    META_ASSERT(GL_DRAW_FRAMEBUFFER == GL_DRAW_FRAMEBUFFER_ANGLE && GL_READ_FRAMEBUFFER == GL_READ_FRAMEBUFFER_ANGLE);
+
+    if (target != GL_FRAMEBUFFER && target != GL_DRAW_FRAMEBUFFER && target != GL_READ_FRAMEBUFFER)
+    {
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
+    if (attachment >= GL_COLOR_ATTACHMENT0 && attachment <= GL_COLOR_ATTACHMENT15)
+    {
+        const unsigned int colorAttachment = (attachment - GL_COLOR_ATTACHMENT0);
+        if (colorAttachment >= context->getMaximumRenderTargets())
+        {
+            return gl::error(GL_INVALID_VALUE, false);
+        }
+    }
+    else
+    {
+        switch (attachment)
+        {
+          case GL_DEPTH_ATTACHMENT:
+          case GL_STENCIL_ATTACHMENT:
+            break;
+          default:
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+    }
+
+    if (texture != 0)
+    {
+        gl::Texture *tex = context->getTexture(texture);
+
+        if (tex == NULL)
+        {
+            return gl::error(GL_INVALID_OPERATION, false);
+        }
+
+        switch (textarget)
+        {
+          case GL_TEXTURE_2D:
+            {
+                if (tex->getTarget() != GL_TEXTURE_2D)
+                {
+                    return gl::error(GL_INVALID_OPERATION, false);
+                }
+                gl::Texture2D *tex2d = static_cast<gl::Texture2D *>(tex);
+                if (tex2d->isCompressed(level))
+                {
+                    return gl::error(GL_INVALID_OPERATION, false);
+                }
+                break;
+            }
+
+          case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
+          case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
+          case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
+          case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
+          case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
+          case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
+            {
+                if (tex->getTarget() != GL_TEXTURE_CUBE_MAP)
+                {
+                    return gl::error(GL_INVALID_OPERATION, false);
+                }
+                gl::TextureCubeMap *texcube = static_cast<gl::TextureCubeMap *>(tex);
+                if (texcube->isCompressed(textarget, level))
+                {
+                    return gl::error(GL_INVALID_OPERATION, false);
+                }
+                break;
+            }
+
+          default:
+            return gl::error(GL_INVALID_ENUM, false);
+        }
+
+        if (level != 0)
+        {
+            return gl::error(GL_INVALID_VALUE, false);
+        }
+    }
+
+    gl::Framebuffer *framebuffer = NULL;
+    GLuint framebufferHandle = 0;
+    if (target == GL_READ_FRAMEBUFFER)
+    {
+        framebuffer = context->getReadFramebuffer();
+        framebufferHandle = context->getReadFramebufferHandle();
+    }
+    else
+    {
+        framebuffer = context->getDrawFramebuffer();
+        framebufferHandle = context->getDrawFramebufferHandle();
+    }
+
+    if (framebufferHandle == 0 || !framebuffer)
+    {
+        return gl::error(GL_INVALID_OPERATION, false);
+    }
+
+    return true;
+}
+
+// check for combinations of format and type that are valid for ReadPixels
+bool validES2ReadFormatType(GLenum format, GLenum type)
+{
+    switch (format)
+    {
+      case GL_RGBA:
+        switch (type)
+        {
+          case GL_UNSIGNED_BYTE:
+            break;
+          default:
+            return false;
+        }
+        break;
+      case GL_BGRA_EXT:
+        switch (type)
+        {
+          case GL_UNSIGNED_BYTE:
+          case GL_UNSIGNED_SHORT_4_4_4_4_REV_EXT:
+          case GL_UNSIGNED_SHORT_1_5_5_5_REV_EXT:
+            break;
+          default:
+            return false;
+        }
+        break;
+      default:
+        return false;
+    }
+    return true;
+}
+
+}