From 9c45b4185ba615e58708c975571dc02da8b03483 Mon Sep 17 00:00:00 2001
From: Scott Chacon <schacon@gmail.com>
Date: Mon, 22 Sep 2008 23:53:22 -0700
Subject: [PATCH] added writing unpacked objects to disk, sha calculations, sha
 packing and unpacking

---
 Git.h              |  8 +++-
 Git.m              | 94 +++++++++++++++++++++++++++++++++++++++++++++-
 GitServerHandler.h |  1 +
 GitServerHandler.m | 14 ++++++-
 4 files changed, 112 insertions(+), 5 deletions(-)

diff --git a/Git.h b/Git.h
index 520986f..aa1108e 100644
--- a/Git.h
+++ b/Git.h
@@ -19,9 +19,13 @@
 - (BOOL) ensureGitPath;
 - (void) initGitRepo;
 
-- (void) writeObject:(NSData *)objectData withType:(int)type withSize:(int)size;
+- (NSString *) writeObject:(NSData *)objectData withType:(NSString *)type withSize:(int)size;
 
 - (NSMutableArray *) getCommitsFromSha:(NSString *)shaValue withLimit:(int)commitSize;
 - (NSString *) getLooseObjectPathBySha:(NSString *)shaValue;
 
-@end
++ (int) isAlpha:(unsigned char)n ;
++ (int) gitUnpackHex:(const unsigned char *)rawsha fillSha:(char *)sha1;
++ (int) gitPackHex:(const char *)sha1 fillRawSha:(unsigned char *)rawsha;
+
+@end
\ No newline at end of file
diff --git a/Git.m b/Git.m
index 005eb51..7d88cfa 100644
--- a/Git.m
+++ b/Git.m
@@ -8,6 +8,8 @@
 #import "GitCommit.h"
 #import "GitServerHandler.h"
 
+#include <CommonCrypto/CommonDigest.h>
+
 @implementation Git
 
 @synthesize gitDirectory;
@@ -55,12 +57,33 @@ - (void) initGitRepo {
 	[fm createDirectoryAtPath:[gitDirectory stringByAppendingPathComponent:@"info"] attributes:nil];
 }
 
-- (void) writeObject:(NSData *)objectData withType:(int)type withSize:(int)size 
+- (NSString *) writeObject:(NSData *)objectData withType:(NSString *)type withSize:(int)size 
 {
 	NSLog(@"WRITE OBJECT");
+	NSMutableData *object;
+	NSString *header, *path, *shaStr;
+	unsigned char rawsha[20];
+	char sha1[41];
+	
+	header = [NSString stringWithFormat:@"%@ %d", type, size];
+	NSLog(@"header: %@", header);
+	
+	const char *headerBytes = [header cStringUsingEncoding:NSASCIIStringEncoding];
+	
+	object = [NSMutableData dataWithBytes:headerBytes length:([header length] + 1)];
+	[object appendData:objectData];
+	
+	CC_SHA1([object bytes], [object length], rawsha);
+	[Git gitUnpackHex:rawsha fillSha:sha1];
+	NSLog(@"SHAR: %s", sha1);
+
+	// write object to file
+	shaStr = [NSString stringWithCString:sha1 encoding:NSASCIIStringEncoding];
+	path = [self getLooseObjectPathBySha:shaStr];
+	[object writeToFile:path atomically:YES];
+	return shaStr;
 }
 
-
 - (BOOL) openRepo:(NSString *)dirPath 
 {
 	gitDirectory = dirPath;
@@ -99,8 +122,75 @@ - (NSString *) getLooseObjectPathBySha: (NSString *)shaValue
 	NSString *looseSubDir   = [shaValue substringWithRange:NSMakeRange(0, 2)];
 	NSString *looseFileName = [shaValue substringWithRange:NSMakeRange(2, 38)];
 	
+	NSString *dir = [NSString stringWithFormat: @"%@/objects/%@", gitDirectory, looseSubDir];
+	
+	BOOL isDir;
+	NSFileManager *fm = [NSFileManager defaultManager];
+	if (!([fm fileExistsAtPath:dir isDirectory:&isDir] && isDir)) {
+		[fm createDirectoryAtPath:dir attributes:nil];
+	}
+	
 	return [NSString stringWithFormat: @"%@/objects/%@/%@", \
 			gitDirectory, looseSubDir, looseFileName];
 }
 
+
+/*
+ * returns 1 if the char is alphanumeric, 0 if not 
+ */
++ (int) isAlpha:(unsigned char)n 
+{
+	if(n <= 102 && n >= 97) {
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * fills a 40-char string with a readable hex version of 20-char sha binary
+ */
++ (int) gitUnpackHex:(const unsigned char *)rawsha fillSha:(char *)sha1
+{
+	static const char hex[] = "0123456789abcdef";
+	int i;
+
+	for (i = 0; i < 20; i++) {          
+		unsigned char n = rawsha[i];
+		sha1[i * 2] = hex[((n >> 4) & 15)];
+		n <<= 4;
+		sha1[(i * 2) + 1] = hex[((n >> 4) & 15)];
+	}
+	sha1[40] = 0;
+	
+	return 1;   
+}
+
+/*
+ * fills 20-char sha from 40-char hex version
+ */
++ (int) gitPackHex:(const char *)sha1 fillRawSha:(unsigned char *)rawsha
+{
+	unsigned char byte = 0;
+	int i, j = 0;
+	
+	for (i = 1; i <= 40; i++) {
+		unsigned char n = sha1[i - 1];
+		
+		if([Git isAlpha:n]) {
+			byte |= ((n & 15) + 9) & 15;
+		} else {
+			byte |= (n & 15);
+		}
+		if(i & 1) {
+			byte <<= 4;
+		} else {
+			rawsha[j] = (byte & 0xff);
+			j++;
+			byte = 0;
+		}
+	}
+	return 1;
+}
+
 @end
+
diff --git a/GitServerHandler.h b/GitServerHandler.h
index f85ad4a..b8516d8 100644
--- a/GitServerHandler.h
+++ b/GitServerHandler.h
@@ -33,6 +33,7 @@
 - (void) readPack;
 - (void) writeRefs;
 - (NSData *) readData:(int)size;
+- (NSString *) typeString:(int)type;
 
 - (int) readPackHeader;
 - (void) unpackObject;
diff --git a/GitServerHandler.m b/GitServerHandler.m
index 6621078..5e935c1 100644
--- a/GitServerHandler.m
+++ b/GitServerHandler.m
@@ -171,7 +171,7 @@ - (void) unpackObject {
 	if((type == OBJ_COMMIT) || (type == OBJ_TREE) || (type == OBJ_BLOB) || (type == OBJ_TAG)) {
 		NSData *objectData;
 		objectData = [self readData:size];
-		[gitRepo writeObject:objectData withType:type withSize:size];
+		[gitRepo writeObject:objectData withType:[self typeString:type] withSize:size];
 		// TODO : check saved delta objects
 	} else if ((type == OBJ_REF_DELTA) || (type == OBJ_OFS_DELTA)) {
 		NSLog(@"NO SUPPORT FOR DELTAS YET");
@@ -180,6 +180,18 @@ - (void) unpackObject {
 	}
 }
 
+- (NSString *) typeString:(int)type {
+	if (type == OBJ_COMMIT) 
+		return @"commit";
+	if (type == OBJ_TREE) 
+		return @"tree";
+	if (type == OBJ_BLOB)
+		return @"blob";
+	if (type == OBJ_TAG)
+		return @"tag";
+	return @"";
+}
+
 - (NSData *) readData:(int)size {
 	// read in the data		
 	NSMutableData *decompressed = [NSMutableData dataWithLength: size];