Fix GCDAsyncSocketPreBuffer availableSpace bugs that lead to access violation.

epatey · epatey · commit 479edd9e321f · 2014-02-10T13:26:29.000-05:00
It's easy to see the bug by putting the read pointer slightly behind the
write pointer both near the end of the buffer.
diff --git a/GCD/GCDAsyncSocket.m b/GCD/GCDAsyncSocket.m
@@ -385,7 +385,7 @@ - (void)dealloc
 
 - (void)ensureCapacityForWrite:(size_t)numBytes
 {
-	size_t availableSpace = preBufferSize - (writePointer - readPointer);
+	size_t availableSpace = [self availableSpace];
 	
 	if (numBytes > availableSpace)
 	{
@@ -418,7 +418,7 @@ - (uint8_t *)readBuffer
 - (void)getReadBuffer:(uint8_t **)bufferPtr availableBytes:(size_t *)availableBytesPtr
 {
 	if (bufferPtr) *bufferPtr = readPointer;
-	if (availableBytesPtr) *availableBytesPtr = writePointer - readPointer;
+	if (availableBytesPtr) *availableBytesPtr = [self availableBytes];
 }
 
 - (void)didRead:(size_t)bytesRead
@@ -435,7 +435,7 @@ - (void)didRead:(size_t)bytesRead
 
 - (size_t)availableSpace
 {
-	return preBufferSize - (writePointer - readPointer);
+	return preBufferSize - (writePointer - preBuffer);
 }
 
 - (uint8_t *)writeBuffer
@@ -446,7 +446,7 @@ - (uint8_t *)writeBuffer
 - (void)getWriteBuffer:(uint8_t **)bufferPtr availableSpace:(size_t *)availableSpacePtr
 {
 	if (bufferPtr) *bufferPtr = writePointer;
-	if (availableSpacePtr) *availableSpacePtr = preBufferSize - (writePointer - readPointer);
+	if (availableSpacePtr) *availableSpacePtr = [self availableSpace];
 }
 
 - (void)didWrite:(size_t)bytesWritten

Original file line number	Diff line number	Diff line change
`@@ -385,7 +385,7 @@ - (void)dealloc`
`385`	`385`
`386`	`386`	`- (void)ensureCapacityForWrite:(size_t)numBytes`
`387`	`387`	`{`
`388`		`- size_t availableSpace = preBufferSize - (writePointer - readPointer);`
	`388`	`+ size_t availableSpace = [self availableSpace];`
`389`	`389`
`390`	`390`	`if (numBytes > availableSpace)`
`391`	`391`	`{`
`@@ -418,7 +418,7 @@ - (uint8_t *)readBuffer`
`418`	`418`	`- (void)getReadBuffer:(uint8_t *)bufferPtr availableBytes:(size_t )availableBytesPtr`
`419`	`419`	`{`
`420`	`420`	`if (bufferPtr) *bufferPtr = readPointer;`
`421`		`- if (availableBytesPtr) *availableBytesPtr = writePointer - readPointer;`
	`421`	`+ if (availableBytesPtr) *availableBytesPtr = [self availableBytes];`
`422`	`422`	`}`
`423`	`423`
`424`	`424`	`- (void)didRead:(size_t)bytesRead`
`@@ -435,7 +435,7 @@ - (void)didRead:(size_t)bytesRead`
`435`	`435`
`436`	`436`	`- (size_t)availableSpace`
`437`	`437`	`{`
`438`		`- return preBufferSize - (writePointer - readPointer);`
	`438`	`+ return preBufferSize - (writePointer - preBuffer);`
`439`	`439`	`}`
`440`	`440`
`441`	`441`	`- (uint8_t *)writeBuffer`
`@@ -446,7 +446,7 @@ - (uint8_t *)writeBuffer`
`446`	`446`	`- (void)getWriteBuffer:(uint8_t *)bufferPtr availableSpace:(size_t )availableSpacePtr`
`447`	`447`	`{`
`448`	`448`	`if (bufferPtr) *bufferPtr = writePointer;`
`449`		`- if (availableSpacePtr) *availableSpacePtr = preBufferSize - (writePointer - readPointer);`
	`449`	`+ if (availableSpacePtr) *availableSpacePtr = [self availableSpace];`
`450`	`450`	`}`
`451`	`451`
`452`	`452`	`- (void)didWrite:(size_t)bytesWritten`