source: releases/Pester/1.1a2/Source/BDAlias.m@ 157

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        disclaimer.
    
    *   Redistributions in binary form must reproduce the above
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        provided with the distribution.
    
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        its contributors may be used to endorse or promote products
        derived from this software without specific prior written
        permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
    CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
    INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
    MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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    OF SUCH DAMAGE.
*/

#include <assert.h>

#import "BDAlias.h"


static Handle DataToHandle(CFDataRef inData);
static CFDataRef HandleToData(Handle inHandle);

static OSStatus PathToFSRef(CFStringRef inPath, FSRef *outRef);
static CFStringRef FSRefToPathCopy(const FSRef *inRef);


static Handle DataToHandle(CFDataRef inData)
{
    CFIndex     len;
    Handle      handle = NULL;
    
    if (inData == NULL) {
        return NULL;
    }
    
    len = CFDataGetLength(inData);
    
    handle = NewHandle(len);
    
    if ((handle != NULL) && (len > 0)) {
        HLock(handle);
        BlockMoveData(CFDataGetBytePtr(inData), *handle, len);
        HUnlock(handle);
    }
    
    return handle;
}

static CFDataRef HandleToData(Handle inHandle)
{
    CFDataRef   data = NULL;
    CFIndex     len;
    SInt8       handleState;
    
    if (inHandle == NULL) {
        return NULL;
    }
    
    len = GetHandleSize(inHandle);
    
    handleState = HGetState(inHandle);
    
    HLock(inHandle);
    
    data = CFDataCreate(kCFAllocatorDefault, (const UInt8 *) *inHandle, len);
    
    HSetState(inHandle, handleState);
    
    return data;
}

static OSStatus PathToFSRef(CFStringRef inPath, FSRef *outRef)
{
    CFURLRef    tempURL = NULL;
    Boolean     gotRef = false;
    
    tempURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, inPath,
                                            kCFURLPOSIXPathStyle, false);
    
    if (tempURL == NULL) {
        return fnfErr;
    }
    
    gotRef = CFURLGetFSRef(tempURL, outRef);
    
    if (gotRef == false) {
        return fnfErr;
    }
    
    return noErr;
}

static CFStringRef FSRefToPathCopy(const FSRef *inRef)
{
    CFURLRef    tempURL = NULL;
    CFStringRef result = NULL;
    
    if (inRef != NULL) {
        tempURL = CFURLCreateFromFSRef(kCFAllocatorDefault, inRef);
        
        if (tempURL == NULL) {
            return NULL;
        }
        
        result = CFURLCopyFileSystemPath(tempURL, kCFURLPOSIXPathStyle);
        
        CFRelease(tempURL);
    }
    
    return result;
}


@implementation BDAlias

- (id)initWithAliasHandle:(AliasHandle)alias
{
    id ret = [super init];
    
    if (ret != nil) {
        _alias = alias;
    }
    
    return ret;
}

- (id)initWithData:(NSData *)data
{
    return [self initWithAliasHandle:(AliasHandle)DataToHandle((CFDataRef) data)];
}

- (id)initWithPath:(NSString *)fullPath
{
    OSStatus    anErr = noErr;
    FSRef               ref;
    
    anErr = PathToFSRef((CFStringRef) fullPath, &ref);
    
    if (anErr != noErr) {
        return nil;
    }
    
    return [self initWithFSRef:&ref];;
}

- (id)initWithPath:(NSString *)path relativeToPath:(NSString *)relPath
{
    OSStatus    anErr = noErr;
    FSRef               ref, relRef;
    
    anErr = PathToFSRef((CFStringRef) [relPath stringByAppendingPathComponent:path],
                        &ref);
    
    if (anErr != noErr) {
        return nil;
    }
    
    anErr = PathToFSRef((CFStringRef) relPath, &relRef);
    
    if (anErr != noErr) {
        return nil;
    }
    
    return [self initWithFSRef:&ref relativeToFSRef:&relRef];
}

- (id)initWithFSRef:(FSRef *)ref
{
    return [self initWithFSRef:ref relativeToFSRef:NULL];
}

- (id)initWithFSRef:(FSRef *)ref relativeToFSRef:(FSRef *)relRef
{
    OSStatus    anErr = noErr;
    AliasHandle alias = NULL;
    
    anErr = FSNewAlias(relRef, ref, &alias);
    
    if (anErr != noErr) {
        return nil;
    }
    
    return [self initWithAliasHandle:alias];
}

- (void)dealloc
{
    if (_alias != NULL) {
        DisposeHandle((Handle) _alias);
        _alias = NULL;
    }
    
    [super dealloc];
}

- (AliasHandle)alias
{
    return _alias;
}

- (void)setAlias:(AliasHandle)newAlias
{
    if (_alias != NULL) {
        DisposeHandle((Handle) _alias);
    }
    
    _alias = newAlias;
}

- (NSData *)aliasData
{
    NSData *result;
    
    result = (NSData *)HandleToData((Handle) _alias);
    
    return [result autorelease];
}

- (void)setAliasData:(NSData *)newAliasData
{
    [self setAlias:(AliasHandle) DataToHandle((CFDataRef) newAliasData)];
}

- (NSString *)fullPath
{
    return [self fullPathRelativeToPath:nil];
}

- (NSString *)fullPathRelativeToPath:(NSString *)relPath
{
    OSStatus    anErr = noErr;
    FSRef       relPathRef;
    FSRef       tempRef;
    NSString    *result = nil;
    Boolean     wasChanged;
    
    if (_alias != NULL) {
        if (relPath != nil) {
            anErr = PathToFSRef((CFStringRef)relPath, &relPathRef);
            
            if (anErr != noErr) {
                return NULL;
            }
            
            anErr = FSResolveAlias(&relPathRef, _alias, &tempRef, &wasChanged);
        } else {
            anErr = FSResolveAlias(NULL, _alias, &tempRef, &wasChanged);
        }
        
        if (anErr != noErr) {
            return NULL;
        }
        
        result = (NSString *)FSRefToPathCopy(&tempRef);
    }
    
    return [result autorelease];
}

- (BOOL)aliasIsEqual:(AliasHandle)otherAlias;
{
    AliasHandle alias = [self alias];
    FSRef ref, otherRef;
    Boolean wasChanged;

    if (alias == otherAlias) return YES;
    if (alias == NULL || otherAlias == NULL) return NO;
    if (FSResolveAlias(NULL, alias, &ref, &wasChanged) != noErr) return NO;
    if (FSResolveAlias(NULL, otherAlias, &otherRef, &wasChanged) != noErr) return NO;
    return (FSCompareFSRefs(&ref, &otherRef) == noErr);
}

- (BOOL)aliasDataIsEqual:(NSData *)data;
{
    AliasHandle otherAlias;
    const UInt8 *aliasPtr = CFDataGetBytePtr((CFDataRef)data);
    BOOL result;
    if (aliasPtr == NULL) {
        otherAlias = (AliasHandle)DataToHandle((CFDataRef)data);
    } else {
        otherAlias = (AliasHandle)&aliasPtr;
    }
    result = [self aliasIsEqual: otherAlias];
    if (aliasPtr == NULL) DisposeHandle((Handle)otherAlias);
    return result;
}

- (BOOL)isEqual:(id)object;
{
    if (![object isKindOfClass: [BDAlias class]]) return NO;
    return [self aliasIsEqual: [object alias]];
}

+ (BDAlias *)aliasWithAliasHandle:(AliasHandle)alias
{
    return [[[BDAlias alloc] initWithAliasHandle:alias] autorelease];
}

+ (BDAlias *)aliasWithData:(NSData *)data
{
    return [[[BDAlias alloc] initWithData:data] autorelease];
}

+ (BDAlias *)aliasWithPath:(NSString *)fullPath
{
    return [[[BDAlias alloc] initWithPath:fullPath] autorelease];
}

+ (BDAlias *)aliasWithPath:(NSString *)path relativeToPath:(NSString *)relPath
{
    return [[[BDAlias alloc] initWithPath:path relativeToPath:relPath] autorelease];
}

+ (BDAlias *)aliasWithFSRef:(FSRef *)ref
{
    return [[[BDAlias alloc] initWithFSRef:ref] autorelease];
}

+ (BDAlias *)aliasWithFSRef:(FSRef *)ref relativeToFSRef:(FSRef *)relRef
{
    return [[[BDAlias alloc] initWithFSRef:ref relativeToFSRef:relRef] autorelease];
}

@end