[原]逆向iOS SDK -- _UIImageAtPath 的实现（SDK 6.1）
汇编代码：
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; 状态：R0 = imageFileName, R1 = mainBundle, R2 = isRetina PUSH {R4-R7,LR} ; R0 = imageFileName, R1 = mainBundle, R2 = isRetina ADD R7, SP, #0xC PUSH.W {R8,R10,R11} STR.W R2, [SP,#0x18+var_1C]! MOV R4, R0 ; R4 = R0 = imageFileName MOV R0, #(selRef_length - 0x17BB0) ; selRef_length MOV R10, R1 ; R10 = R1 = mainBundle ADD R0, PC ; selRef_length LDR R1, [R0] ; "length" MOV R0, R4 ; R0 = R4 = imageFileName BLX.W _objc_msgSend ; [imageFileName length] MOVS R6, #0 ; R6 = 0 CMP R0, #0 ; check if R0 is 0 BEQ.W loc_17D1C ; if R0 is 0, goto the label MOV R0, R4 ; R0 = R4 = imageFileName MOV R1, R10 ; R1 = R10 = mainBundle BL __UICacheNameForImageAtPath ; arg_0:imageFileName, arg_1:mainBundle, result:com.proteas.hello_Default.png MOVW R8, #(:lower16:(__MergedGlobals_36 - 0x17BD4)) MOV R5, R0 ; R5 = R0 = imageCacheName MOVT.W R8, #(:upper16:(__MergedGlobals_36 - 0x17BD4)) ADD R8, PC ; __MergedGlobals_36 ADD.W R11, R8, #0x10 ; R11 = R8 + 16 MOV R0, R11 ; lock, OSSpinLock*, 访问全局变量，加锁 BLX.W _OSSpinLockLock ; arg_0: OSSpinLock* LDR.W R0, [R8,#(dword_62C524 - 0x62C510)] ; R0 = cachedImageMap, key:imageCacheName, value:UIImageObject MOVS R6, #0 ; R6 = 0 CBZ R0, loc_17BEC ; if cachedImageMap is nil, goto the label MOV R1, R5 ; R1 = R5 = imageCacheName BLX.W _CFDictionaryGetValue ; CFDictionaryGetValue(cachedImageMap, imageCacheName) MOV R6, R0 ; R6 = R0 = cachedUIImageObject loc_17BEC: MOV R0, #(selRef_retainCount - 0x17BF8) ; selRef_retainCount ADD R0, PC ; selRef_retainCount LDR R1, [R0] ; "retainCount" MOV R0, R6 ; R0 = R6 = cachedUIImageObject BLX.W _objc_msgSend ; [cachedUIImageObject retainCount] CBNZ R0, loc_17C08 ; if retainCount of cachedUIImageObject is not 0, goto the label MOV R0, R11 ; lock BLX.W _OSSpinLockUnlock B loc_17C50 loc_17C08: MOV R0, #(selRef__isCached - 0x17C14) ; selRef__isCached ADD R0, PC ; selRef__isCached LDR R1, [R0] ; R1 = "_isCached" MOV R0, R6 ; R0 = R6 = cachedUIImageObject BLX.W _objc_msgSend ; R0 = isCached TST.W R0, #0xFF ; check if R0 is true BNE loc_17C46 ; if not cached, goto the label MOV R0, #(selRef_retain - 0x17C2C) ; selRef_retain ADD R0, PC ; selRef_retain LDR R1, [R0] ; "retain" MOV R0, R6 ; R0 = R6 = cachedUIImageObject BLX.W _objc_msgSend ; [cachedUIImageObject retain] MOVW R0, #(:lower16:(selRef__setCached_ - 0x17C40)) MOVS R2, #1 ; R2 = 1 MOVT.W R0, #(:upper16:(selRef__setCached_ - 0x17C40)) ADD R0, PC ; selRef__setCached_ LDR R1, [R0] ; "_setCached:" MOV R0, R6 ; R0 = R6 = cachedUIImageObject BLX.W _objc_msgSend ; [cachedUIImageObject _setCached:YES] loc_17C46: MOV R0, R11 ; lock BLX.W _OSSpinLockUnlock ; 释放锁 CMP R6, #0 ; check if cachedUIImageObject is nil BNE loc_17D1C ; if not nil, goto the label loc_17C50: MOVW R3, #(:lower16:(_GetImageAtPath+1 - 0x17C60)) MOV R0, R4 ; R0 = R4 = imageFileName MOVT.W R3, #(:upper16:(_GetImageAtPath+1 - 0x17C60)) LDR R2, [SP,#0x1C+var_1C] ; R2 = isRetina ADD R3, PC ; _GetImageAtPath ; R3 = _GetImageAtPath MOV R1, R10 ; R1 = R10 = mainBundle BL __UIImageCallFunctionForAppropriatePath ; arg_0:imageFileName, arg_1 = mainBundle, arg_2 = isRetina, arg_3 = _GetImageAtPath MOV R6, R0 ; R6 = R0 = UIImageObject CMP R6, #0 ; check if UIImageObject is nil BEQ loc_17D1C ; if failed, goto label MOV R0, R11 ; lock BLX.W _OSSpinLockLock LDR.W R0, [R8,#0x14] ; R0 = pointer to imageCacheMap CBNZ R0, loc_17CAE ; R1 = R5 = imageCacheName MOVW R0, #(:lower16:(_kCFTypeDictionaryKeyCallBacks_ptr - 0x17C86)) MOVS R1, #0 ; R1 = capacity = 0 MOVT.W R0, #(:upper16:(_kCFTypeDictionaryKeyCallBacks_ptr - 0x17C86)) MOVS R3, #0 ; R3 = valueCallBacks = 0 ADD R0, PC ; _kCFTypeDictionaryKeyCallBacks_ptr LDR R2, [R0] ; _kCFTypeDictionaryKeyCallBacks MOVS R0, #0 ; R0 = allocator = NULL BLX.W _CFDictionaryCreateMutable ; R0 = cachedImageMap MOVW R1, #(:lower16:(_kCFTypeDictionaryValueCallBacks_ptr - 0x17C9E)) MOVS R2, #0 ; R2 = keyCallBacks = NULL MOVT.W R1, #(:upper16:(_kCFTypeDictionaryValueCallBacks_ptr - 0x17C9E)) STR.W R0, [R8,#0x14] ADD R1, PC ; _kCFTypeDictionaryValueCallBacks_ptr MOVS R0, #0 ; R0 = allocator = NULL LDR R3, [R1] ; _kCFTypeDictionaryValueCallBacks MOVS R1, #0 ; R1 = capacity = 0 BLX.W _CFDictionaryCreateMutable STR.W R0, [R8,#0x18] LDR.W R0, [R8,#0x14] loc_17CAE: MOV R1, R5 ; R1 = R5 = imageCacheName BLX.W _CFDictionaryContainsKey CBNZ R0, loc_17CF8 ; if has cached, goto the label MOVW R0, #(:lower16:(selRef__setNamed_ - 0x17CC4)) MOVS R2, #1 ; R2 = YES MOVT.W R0, #(:upper16:(selRef__setNamed_ - 0x17CC4)) ADD R0, PC ; selRef__setNamed_ LDR R1, [R0] ; "_setNamed:" MOV R0, R6 ; R0 = R6 = UIImageObject BLX.W _objc_msgSend ; [UIImageObject _setNamed:YES] MOVW R0, #(:lower16:(selRef__setCached_ - 0x17CD8)) MOVS R2, #1 MOVT.W R0, #(:upper16:(selRef__setCached_ - 0x17CD8)) ADD R0, PC ; selRef__setCached_ LDR R1, [R0] ; "_setCached:" MOV R0, R6 BLX.W _objc_msgSend ; [UIImageObject _setCached:YES] LDR.W R0, [R8,#0x14] ; R0 = cachedImageMap MOV R1, R5 ; R1 = R5 = imageCacheName MOV R2, R6 ; R2 = R6 = UIImageObject BLX.W _CFDictionarySetValue ; arg_0:cachedImageMap, arg_1 = imageCacheName, arg_2 = imageObject LDR.W R0, [R8,#0x18] MOV R1, R6 ; R1 = R6 = UIImageObject MOV R2, R5 ; R2 = R5 = imageCacheName BLX.W _CFDictionarySetValue ; arg_0: dictionary, arg_1: imageObject, arg_2 = imageCacheName B loc_17D16 loc_17CF8: MOV R0, #(selRef_release - 0x17D04) ; selRef_release ADD R0, PC ; selRef_release LDR R1, [R0] ; "release" MOV R0, R6 ; R0 = R6 = UIImageObject BLX.W _objc_msgSend ; [UIImageObject release] LDR.W R0, [R8,#0x14] ; R0 = cachedImageMap MOV R1, R5 ; R1 = R5 = imageCacheName BLX.W _CFDictionaryGetValue MOV R6, R0 ; R6 = R0 = result UIImage instance loc_17D16: MOV R0, R11 ; lock BLX.W _OSSpinLockUnlock ; release spin lock loc_17D1C: MOV R0, R6 ; R0 = R6 = nil ADD SP, SP, #4 POP.W {R8,R10,R11} POP {R4-R7,PC} |
伪代码：
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NSDictionary *gCachedImageMapNameToImage = nil; NSDictionary *gCachedImageMapImageToName = nil;
_UIImageAtPath(NSString *imageFileName, NSBundle *mainBundle, BOOL isRetina) { if ([imageFileName length] == 0) returnnil;
if (gCachedImageMapNameToImage == nil) { gCachedImageMapNameToImage = [[NSMutableDictionaryalloc] init]; gCachedImageMapImageToName = [[NSMutableDictionaryalloc] init]; }
NSString *imageCacheName = _UICacheNameForImageAtPath(imageFileName, mainBundle); UIImage *cachedImage = [gCachedImageMapNameToImageobjectForKey:imageCacheName]; if (cachedImage == nil) { cachedImage = _UIImageCallFunctionForAppropriatePath(imageFileName, mainBundle, isRetina, _UIImageAtPath); if (cachedImage == nil) { returnnil; } else { [gCachedImageMapNameToImagesetObject:cachedImage forKey:imageCacheName]; [gCachedImageMapImageToNamesetObject:imageCacheName forKey:cachedImage];
[cachedImage _setNamed:YES]; [cachedImage _setCached:YES]; } } else { if (![cachedImage _isCached]) { [cachedImage _setCached:YES]; } } return cachedImage; } |