From 3c2c129cadcbc26ab70ee770cd35c71b75ae751f Mon Sep 17 00:00:00 2001
From: Scott Schneider <scott.a.s@gmail.com>
Date: Wed, 6 Nov 2024 12:44:11 -0500
Subject: [PATCH] Account for current pointer being outside of the buffer

Differential Revision: D65118896

Pull Request resolved: https://github.com/pytorch/torchcodec/pull/316
---
 src/torchcodec/decoders/_core/FFMPEGCommon.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/torchcodec/decoders/_core/FFMPEGCommon.cpp b/src/torchcodec/decoders/_core/FFMPEGCommon.cpp
index 8d2c1c03..ab50414f 100644
--- a/src/torchcodec/decoders/_core/FFMPEGCommon.cpp
+++ b/src/torchcodec/decoders/_core/FFMPEGCommon.cpp
@@ -69,6 +69,12 @@ AVIOContext* AVIOBytesContext::getAVIO() {
 int AVIOBytesContext::read(void* opaque, uint8_t* buf, int buf_size) {
   struct AVIOBufferData* bufferData =
       static_cast<struct AVIOBufferData*>(opaque);
+  TORCH_CHECK(
+      bufferData->current <= bufferData->size,
+      "Tried to read outside of the buffer: current=",
+      bufferData->current,
+      ", size=",
+      bufferData->size);
   buf_size = FFMIN(buf_size, bufferData->size - bufferData->current);
   TORCH_CHECK(
       buf_size >= 0,