From 1d7de2c00dae782992e1c082fbf3e98fe3666b88 Mon Sep 17 00:00:00 2001
From: rowanbeentje <rowan@beent.je>
Date: Mon, 26 Apr 2010 23:42:32 +0000
Subject:  - Improve threading of SPFileHandle to achieve much faster writing
 due to increased separation of the writing thread. This results in a up-to
 1.2x faster MySQL dump for fast servers, and makes SPFileHandle faster than
 NSFileHandle for writing data (either directly or GZIP compressed).

---
 Source/SPFileHandle.h |  1 +
 Source/SPFileHandle.m | 39 ++++++++++++++++++++++++++++++---------
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/Source/SPFileHandle.h b/Source/SPFileHandle.h
index 05a8da0e..05e05dd5 100644
--- a/Source/SPFileHandle.h
+++ b/Source/SPFileHandle.h
@@ -44,6 +44,7 @@
 
 	int fileMode;
 	BOOL dataWritten;
+	BOOL allDataWritten;
 	BOOL fileIsClosed;
 	BOOL useGzip;
 }
diff --git a/Source/SPFileHandle.m b/Source/SPFileHandle.m
index e0838a6d..bceae2aa 100644
--- a/Source/SPFileHandle.m
+++ b/Source/SPFileHandle.m
@@ -51,6 +51,8 @@
 - (id) initWithFile:(void *)theFile fromPath:(const char *)path mode:(int)mode
 {
 	if (self = [super init]) {
+		dataWritten = NO;
+		allDataWritten = YES;
 		fileIsClosed = NO;
 
 		wrappedFile = theFile;
@@ -216,9 +218,12 @@
 	if (fileIsClosed) [NSException raise:NSInternalInconsistencyException format:@"Cannot write to a file handle after it has been closed"];
 
 	// Add the data to the buffer
-	pthread_mutex_lock(&bufferLock);
-	[buffer appendData:data];
-	bufferDataLength += [data length];
+	if ([data length]) {
+		pthread_mutex_lock(&bufferLock);
+		[buffer appendData:data];
+		allDataWritten = NO;
+		bufferDataLength += [data length];
+	}
 
 	// If the buffer is large, wait for some to be written out
 	while (bufferDataLength > SPFH_MAX_WRITE_BUFFER_SIZE) {
@@ -235,7 +240,7 @@
 - (void) synchronizeFile
 {
 	pthread_mutex_lock(&bufferLock);
-	while (bufferDataLength) {
+	while (!allDataWritten) {
 		pthread_mutex_unlock(&bufferLock);
 		usleep(100);
 		pthread_mutex_lock(&bufferLock);
@@ -302,17 +307,33 @@
 			continue;
 		}
 
+		// Copy the data into a local buffer
+		NSData *dataToBeWritten = [NSData dataWithData:buffer];
+		[buffer setLength:0];
+		bufferDataLength = 0;
+		pthread_mutex_unlock(&bufferLock);
+
 		// Write out the data
 		long bufferLengthWrittenOut;
 		if (useGzip) {
-			bufferLengthWrittenOut = gzwrite(wrappedFile, [buffer bytes], bufferDataLength);
+			bufferLengthWrittenOut = gzwrite(wrappedFile, [dataToBeWritten bytes], [dataToBeWritten length]);
 		} else {
-			bufferLengthWrittenOut = fwrite([buffer bytes], 1, bufferDataLength, wrappedFile);
+			bufferLengthWrittenOut = fwrite([dataToBeWritten bytes], 1, [dataToBeWritten length], wrappedFile);
 		}
 
-		// Update the buffer
-		CFDataDeleteBytes((CFMutableDataRef)buffer, CFRangeMake(0, bufferLengthWrittenOut));
-		bufferDataLength = 0;
+		// Restore data to the buffer if it wasn't written out
+		pthread_mutex_lock(&bufferLock);
+		if (bufferLengthWrittenOut < [dataToBeWritten length]) {
+			if ([buffer length]) {
+				long dataLengthToRestore = [dataToBeWritten length] - bufferLengthWrittenOut;
+				[buffer replaceBytesInRange:NSMakeRange(0, 0) withBytes:[[dataToBeWritten subdataWithRange:NSMakeRange(bufferLengthWrittenOut, dataLengthToRestore)] bytes] length:dataLengthToRestore];
+				bufferDataLength += dataLengthToRestore;
+			}
+
+		// Otherwise, mark all data as written if it has been - allows synching to hard disk.
+		} else if (![buffer length]) {
+			allDataWritten = YES;
+		}
 		pthread_mutex_unlock(&bufferLock);
 	}
 
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