void WebGL2Context::GetBufferSubDataT(GLenum target, GLintptr offset, const BufferT& data) { if (IsContextLost()) return; // For the WebGLBuffer bound to the passed target, read // returnedData.byteLength bytes from the buffer starting at byte // offset offset and write them to returnedData. // If zero is bound to target, an INVALID_OPERATION error is // generated. if (!ValidateBufferTarget(target, "getBufferSubData")) return; // If offset is less than zero, an INVALID_VALUE error is // generated. if (offset < 0) return ErrorInvalidValue("getBufferSubData: negative offset"); WebGLRefPtr<WebGLBuffer>& bufferSlot = GetBufferSlotByTarget(target); WebGLBuffer* boundBuffer = bufferSlot.get(); if (!boundBuffer) return ErrorInvalidOperation("getBufferSubData: no buffer bound"); // If offset + returnedData.byteLength would extend beyond the end // of the buffer an INVALID_VALUE error is generated. data.ComputeLengthAndData(); CheckedInt<WebGLsizeiptr> neededByteLength = CheckedInt<WebGLsizeiptr>(offset) + data.LengthAllowShared(); if (!neededByteLength.isValid()) { ErrorInvalidValue("getBufferSubData: Integer overflow computing the needed" " byte length."); return; } if (neededByteLength.value() > boundBuffer->ByteLength()) { ErrorInvalidValue("getBufferSubData: Not enough data. Operation requires" " %d bytes, but buffer only has %d bytes.", neededByteLength.value(), boundBuffer->ByteLength()); return; } // If target is TRANSFORM_FEEDBACK_BUFFER, and any transform // feedback object is currently active, an INVALID_OPERATION error // is generated. WebGLTransformFeedback* currentTF = mBoundTransformFeedback; if (target == LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER && currentTF) { if (currentTF->mIsActive) return ErrorInvalidOperation("getBufferSubData: Currently bound transform" " feedback is active"); // https://github.com/NVIDIA/WebGL/commit/63aff5e58c1d79825a596f0f4aa46174b9a5f72c // Performing reads and writes on a buffer that is currently // bound for transform feedback causes undefined results in // GLES3.0 and OpenGL 4.5. In practice results of reads and // writes might be consistent as long as transform feedback // objects are not active, but neither GLES3.0 nor OpenGL 4.5 // spec guarantees this - just being bound for transform // feedback is sufficient to cause undefined results. BindTransformFeedback(LOCAL_GL_TRANSFORM_FEEDBACK, nullptr); } /* If the buffer is written and read sequentially by other * operations and getBufferSubData, it is the responsibility of * the WebGL API to ensure that data are access * consistently. This applies even if the buffer is currently * bound to a transform feedback binding point. */ void* ptr = gl->fMapBufferRange(target, offset, data.LengthAllowShared(), LOCAL_GL_MAP_READ_BIT); // Warning: Possibly shared memory. See bug 1225033. memcpy(data.DataAllowShared(), ptr, data.LengthAllowShared()); gl->fUnmapBuffer(target); if (target == LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER && currentTF) { BindTransformFeedback(LOCAL_GL_TRANSFORM_FEEDBACK, currentTF); } }