Comment lire les données de NSFileHandle ligne par ligne?

Question

J'ai un fichier texte ayant les données comme données

par exemple. 

PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV
PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV

Maintenant, je veux lire les données ligne par ligne. Cela signifie d'abord que je veux lire

PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV

et ensuite, il reste encore ... tout le monde a une idée ??

Answer 1

Si votre fichier est petit, alors la méthode de @ mipadi sera probablement très bien. Toutefois, si votre fichier est volumineux (> 1 Mo, peut-être?), Vous pouvez envisager de le lire ligne par ligne. J'ai écrit un cours une fois pour le faire, que je vais coller ici:

//DDFileReader.h

@interface DDFileReader : NSObject {
    NSString * filePath;

    NSFileHandle * fileHandle;
    unsigned long long currentOffset;
    unsigned long long totalFileLength;

    NSString * lineDelimiter;
    NSUInteger chunkSize;
}

@property (nonatomic, copy) NSString * lineDelimiter;
@property (nonatomic) NSUInteger chunkSize;

- (id) initWithFilePath:(NSString *)aPath;

- (NSString *) readLine;
- (NSString *) readTrimmedLine;

#if NS_BLOCKS_AVAILABLE
- (void) enumerateLinesUsingBlock:(void(^)(NSString*, BOOL *))block;
#endif

@end


//DDFileReader.m

#import "DDFileReader.h"

@interface NSData (DDAdditions)

- (NSRange) rangeOfData_dd:(NSData *)dataToFind;

@end

@implementation NSData (DDAdditions)

- (NSRange) rangeOfData_dd:(NSData *)dataToFind {

    const void * bytes = [self bytes];
    NSUInteger length = [self length];

    const void * searchBytes = [dataToFind bytes];
    NSUInteger searchLength = [dataToFind length];
    NSUInteger searchIndex = 0;

    NSRange foundRange = {NSNotFound, searchLength};
    for (NSUInteger index = 0; index < length; index++) {
        if (((char *)bytes)[index] == ((char *)searchBytes)[searchIndex]) {
            //the current character matches
            if (foundRange.location == NSNotFound) {
                foundRange.location = index;
            }
            searchIndex++;
            if (searchIndex >= searchLength) { return foundRange; }
        } else {
            searchIndex = 0;
            foundRange.location = NSNotFound;
        }
    }
    return foundRange;
}

@end

@implementation DDFileReader
@synthesize lineDelimiter, chunkSize;

- (id) initWithFilePath:(NSString *)aPath {
    if (self = [super init]) {
        fileHandle = [NSFileHandle fileHandleForReadingAtPath:aPath];
        if (fileHandle == nil) {
            [self release]; return nil;
        }

        lineDelimiter = [[NSString alloc] initWithString:@"\n"];
        [fileHandle retain];
        filePath = [aPath retain];
        currentOffset = 0ULL;
        chunkSize = 10;
        [fileHandle seekToEndOfFile];
        totalFileLength = [fileHandle offsetInFile];
        //we don't need to seek back, since readLine will do that.
    }
    return self;
}

- (void) dealloc {
    [fileHandle closeFile];
    [fileHandle release], fileHandle = nil;
    [filePath release], filePath = nil;
    [lineDelimiter release], lineDelimiter = nil;
    currentOffset = 0ULL;
    [super dealloc];
}

- (NSString *) readLine {
    if (currentOffset >= totalFileLength) { return nil; }

    NSData * newLineData = [lineDelimiter dataUsingEncoding:NSUTF8StringEncoding];
    [fileHandle seekToFileOffset:currentOffset];
    NSMutableData * currentData = [[NSMutableData alloc] init];
    BOOL shouldReadMore = YES;

    NSAutoreleasePool * readPool = [[NSAutoreleasePool alloc] init];
    while (shouldReadMore) {
        if (currentOffset >= totalFileLength) { break; }
        NSData * chunk = [fileHandle readDataOfLength:chunkSize];
        NSRange newLineRange = [chunk rangeOfData_dd:newLineData];
        if (newLineRange.location != NSNotFound) {

            //include the length so we can include the delimiter in the string
            chunk = [chunk subdataWithRange:NSMakeRange(0, newLineRange.location+[newLineData length])];
            shouldReadMore = NO;
        }
        [currentData appendData:chunk];
        currentOffset += [chunk length];
    }
    [readPool release];

    NSString * line = [[NSString alloc] initWithData:currentData encoding:NSUTF8StringEncoding];
    [currentData release];
    return [line autorelease];
}

- (NSString *) readTrimmedLine {
    return [[self readLine] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}

#if NS_BLOCKS_AVAILABLE
- (void) enumerateLinesUsingBlock:(void(^)(NSString*, BOOL*))block {
  NSString * line = nil;
  BOOL stop = NO;
  while (stop == NO && (line = [self readLine])) {
    block(line, &stop);
  }
}
#endif

@end

Ensuite, pour utiliser ceci, vous feriez:

DDFileReader * reader = [[DDFileReader alloc] initWithFilePath:pathToMyFile];
NSString * line = nil;
while ((line = [reader readLine])) {
  NSLog(@"read line: %@", line);
}
[reader release];

Ou (pour 10.6+ et iOS 4+):

DDFileReader * reader = [[DDFileReader alloc] initWithFilePath:pathToMyFile];
[reader enumerateLinesUsingBlock:^(NSString * line, BOOL * stop) {
  NSLog(@"read line: %@", line);
}];
[reader release];

Joyeux Noël. :)

Answer 2

J'ai réécrit ceci pour qu'il soit conforme à l'ARC:

//
//  DDFileReader.m
//  PBX2OPML
//
//  Created by michael isbell on 11/6/11.
//  Copyright (c) 2011 BlueSwitch. All rights reserved.
//

//DDFileReader.m

#import "DDFileReader.h"

@interface NSData (DDAdditions)

- (NSRange) rangeOfData_dd:(NSData *)dataToFind;

@end

@implementation NSData (DDAdditions)

- (NSRange) rangeOfData_dd:(NSData *)dataToFind {

    const void * bytes = [self bytes];
    NSUInteger length = [self length];

    const void * searchBytes = [dataToFind bytes];
    NSUInteger searchLength = [dataToFind length];
    NSUInteger searchIndex = 0;

    NSRange foundRange = {NSNotFound, searchLength};
    for (NSUInteger index = 0; index < length; index++) {
        if (((char *)bytes)[index] == ((char *)searchBytes)[searchIndex]) {
            //the current character matches
            if (foundRange.location == NSNotFound) {
                foundRange.location = index;
            }
            searchIndex++;
            if (searchIndex >= searchLength) { return foundRange; }
        } else {
            searchIndex = 0;
            foundRange.location = NSNotFound;
        }
    }
    return foundRange;
}

@end

@implementation DDFileReader
@synthesize lineDelimiter, chunkSize;

- (id) initWithFilePath:(NSString *)aPath {
    if (self = [super init]) {
        fileHandle = [NSFileHandle fileHandleForReadingAtPath:aPath];
        if (fileHandle == nil) {
            return nil;
        }

        lineDelimiter = @"\n";
        currentOffset = 0ULL; // ???
        chunkSize = 10;
        [fileHandle seekToEndOfFile];
        totalFileLength = [fileHandle offsetInFile];
        //we don't need to seek back, since readLine will do that.
    }
    return self;
}

- (void) dealloc {
    [fileHandle closeFile];
    currentOffset = 0ULL;

}

- (NSString *) readLine {
    if (currentOffset >= totalFileLength) { return nil; }

    NSData * newLineData = [lineDelimiter dataUsingEncoding:NSUTF8StringEncoding];
    [fileHandle seekToFileOffset:currentOffset];
    NSMutableData * currentData = [[NSMutableData alloc] init];
    BOOL shouldReadMore = YES;

    @autoreleasepool {

    while (shouldReadMore) {
        if (currentOffset >= totalFileLength) { break; }
        NSData * chunk = [fileHandle readDataOfLength:chunkSize];
        NSRange newLineRange = [chunk rangeOfData_dd:newLineData];
        if (newLineRange.location != NSNotFound) {

            //include the length so we can include the delimiter in the string
            chunk = [chunk subdataWithRange:NSMakeRange(0, newLineRange.location+[newLineData length])];
            shouldReadMore = NO;
        }
        [currentData appendData:chunk];
        currentOffset += [chunk length];
    }
    }

    NSString * line = [[NSString alloc] initWithData:currentData encoding:NSUTF8StringEncoding];
    return line;  
}

- (NSString *) readTrimmedLine {
    return [[self readLine] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}

#if NS_BLOCKS_AVAILABLE
- (void) enumerateLinesUsingBlock:(void(^)(NSString*, BOOL*))block {
    NSString * line = nil;
    BOOL stop = NO;
    while (stop == NO && (line = [self readLine])) {
        block(line, &stop);
    }
}
#endif

@end

Answer 3

J'ai commencé un projet GitHub basé sur le code source de Dave DeLong . Vous êtes invités à améliorer le code. Je peux maintenant lire les fichiers dans les deux sens.

Answer 4

NSString *fh = [NSString stringWithContentsOfFile:filePath encoding:fileEncoding error:NULL];
for (NSString *line in [fh componentsSeparatedByString:@"\n"]) {
    // Do something with the line
}

Il n'y a pas d'API dans Cocoa, ni de constructions de langage intégrées, pour lire un fichier ligne par ligne.

Answer 5

Voici une méthode que j'ai utilisée pour lire une ligne individuelle à partir d'un NSInputStream. Notez qu'il est optimisé pour la lisibilité et non pour la vitesse. ;-)

- (NSString*) readLine: (NSInputStream*) inputStream {
    NSMutableData* data = [NSMutableData data];
    uint8_t oneByte;
    do {
        int actuallyRead = [inputStream read: &oneByte maxLength: 1];
        if (actuallyRead == 1) {
            [data appendBytes: &oneByte length: 1];
        }        
    } while (oneByte != '\n');

    return [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];

Answer 6

La réponse à cette question pour les fichiersVOLUMINEUXne nécessite pas de fonction personnalisée. Objective-C est un sur-ensemble de c et a donc les méthodes c pour le faire.

FILE* file = fopen("path to my file", "r");

size_t length;
char *cLine = fgetln(file,&length);

while (length>0) {
    char str[length+1];
    strncpy(str, cLine, length);
    str[length] = '\0';

    NSString *line = [NSString stringWithFormat:@"%s",str];        
    % Do what you want here.

    cLine = fgetln(file,&length);
}

Notez que fgetln ne conservera pas votre caractère de nouvelle ligne. De plus, nous +1 la longueur de la chaîne parce que nous voulons faire de la place pour la terminaison NULL.

Answer 7

J'ai découvert que GitX utilise également un lecteur de lignes.
Consultez le répertoire de brotherbard sur GitHub ou le site Web de Michael Stapelberg . 

@ Joe Yang
Agréable! Je vais regarder de plus près les prochains jours.
Je serais heureux si vous voulez forkmon référentiel sur GitHub et envoyez-moi une demande d'extraction.

Answer 8

Vous pouvez également consulter la bibliothèque CGIStream que j'ai créée pour mon projet de serveur HTTP à l'adresse https://github.com/xcvista/ohttpd2/tree/master/CGIStream . Au lieu de descripteurs de fichier, ce code fonctionne sur NSInputStream. Il s'agit essentiellement d'un clone Objective-C de System.IO.StreamReader et System.IO.StreamWriter du framework .net de Microsoft.

Cela fonctionnera non seulement avec les fichiers mais aussi avec les sockets réseau. Je l'utilise pour gérer le protocole HTTP, qui porte le nom du préfixe CGI.

Answer 9

J'ai modifié FileReader en une catégorie NSFileHandle. J'espère que cela pourra aider les autres

@interface NSFileHandle (Readline)
- (NSString*)readLine;
- (NSString*)readLineBackwards;
@end

#import "NSFileHandle+Readline.h"
#import "NSDataExtensions.h"

@implementation NSFileHandle (Readline)

- (NSString*)readLine {

    NSString * _lineDelimiter = @"\n";

    NSData* newLineData = [_lineDelimiter dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData* currentData = [[NSMutableData alloc] init];
    BOOL shouldReadMore = YES;

    NSUInteger _chunkSize = 10;

    while (shouldReadMore) {
        NSData* chunk = [self readDataOfLength:_chunkSize]; // always length = 10

        if ([chunk length] == 0) {
            break;
        }

        // Find the location and length of the next line delimiter.
        NSRange newLineRange = [chunk rangeOfData:newLineData];
        if (newLineRange.location != NSNotFound) {
            // Include the length so we can include the delimiter in the string.
            NSRange subDataRange = NSMakeRange(0, newLineRange.location + [newLineData length]);
            unsigned long long newOffset = [self offsetInFile] - [chunk length] + newLineRange.location + [newLineData length];
            [self seekToFileOffset:newOffset];
            chunk = [chunk subdataWithRange:subDataRange];
            shouldReadMore = NO;
        }
        [currentData appendData:chunk];
    }

    NSString* line = [currentData stringValueWithEncoding:NSASCIIStringEncoding];
    return line;
}

- (NSString*)readLineBackwards {

    NSString * _lineDelimiter = @"\n";

    NSData* newLineData = [_lineDelimiter dataUsingEncoding:NSUTF8StringEncoding];
    NSUInteger _chunkSize = 10;

    NSMutableData* currentData = [[NSMutableData alloc] init];
    BOOL shouldReadMore = YES;

    while (shouldReadMore) {

        unsigned long long offset;

        NSUInteger currentChunkSize = _chunkSize;

        if ([self offsetInFile] <= _chunkSize) {
            offset = 0;
            currentChunkSize = [self offsetInFile];
            shouldReadMore = NO;
        } else {
            offset = [self offsetInFile] - _chunkSize;
        }

        NSLog(@"seek to offset %qu, offset in file is %qu", offset, [self offsetInFile]);

        [self seekToFileOffset:offset];

        NSData* chunk = [self readDataOfLength:currentChunkSize];

        NSRange newLineRange = [chunk rangeOfDataBackwardsSearch:newLineData];

        if (newLineRange.location == NSNotFound) {
            [self seekToFileOffset:offset];
        }

        if (newLineRange.location != NSNotFound) {
            NSUInteger subDataLoc = newLineRange.location;
            NSUInteger subDataLen = currentChunkSize - subDataLoc;
            chunk = [chunk subdataWithRange:NSMakeRange(subDataLoc, subDataLen)];
            NSLog(@"got chunk data %@", [chunk stringValueWithEncoding:NSASCIIStringEncoding]);
            shouldReadMore = NO;
            [self seekToFileOffset:offset + newLineRange.location];
        }
        [currentData prepend:chunk];
    }

    NSString* line = [[NSString alloc] initWithData:currentData encoding:NSASCIIStringEncoding];
    return [line autorelease];
}

@end





//
//  NSDataExtensions.m
//  LineReader
//
//  Created by Tobias Preuss on 08.10.10.
//  Copyright 2010 Tobias Preuss. All rights reserved.
//

#import "NSDataExtensions.h"



// -----------------------------------------------------------------------------
// NSData additions.
// -----------------------------------------------------------------------------


/**
 Extension of the NSData class. 
 Data can be found forwards or backwards. Further the extension supplies a function 
 to convert the contents to string for debugging purposes.
 @param Additions Category labeled Additions.
 @returns An initialized NSData object or nil if the object could not be created.
 */
@implementation NSData (Additions)




/**
 Returns a range of data.
 @param dataToFind Data object specifying the delimiter and encoding.
 @returns A range.
 */
- (NSRange)rangeOfData:(NSData*)dataToFind {

    const void* bytes = [self bytes];
    NSUInteger length = [self length];
    const void* searchBytes = [dataToFind bytes];
    NSUInteger searchLength = [dataToFind length];
    NSUInteger searchIndex = 0;

    NSRange foundRange = {NSNotFound, searchLength};
    for (NSUInteger index = 0; index < length; index++) {
        // The current character matches.
        if (((char*)bytes)[index] == ((char*)searchBytes)[searchIndex]) {
            // Store found location if not done earlier.
            if (foundRange.location == NSNotFound) {
                foundRange.location = index;
            }
            // Increment search character index to check for match.
            searchIndex++;
            // All search character match.
            // Break search routine and return found position.
            if (searchIndex >= searchLength) {
                return foundRange;
            }
        }
        // Match does not continue.
        // Return to the first search character.
        // Discard former found location.
        else {
            searchIndex = 0;
            foundRange.location = NSNotFound;
        }
    }
    return foundRange;
}


- (NSRange)rangeOfDataBackwardsSearch:(NSData*)dataToFind {

    const void* bytes = [self bytes];
    NSUInteger length = [self length];
    const void* searchBytes = [dataToFind bytes];
    NSUInteger searchLength = [dataToFind length];
    NSUInteger searchIndex = 0;

    NSRange foundRange = {NSNotFound, searchLength};
    if (length < searchLength) {
        return foundRange;
    }
    for (NSUInteger index = length - searchLength; index >= 0;) {
//      NSLog(@"%c == %c", ((char*)bytes)[index], ((char*)searchBytes)[searchIndex]); /* DEBUG LOG */
        if (((char*)bytes)[index] == ((char*)searchBytes)[searchIndex]) {
            // The current character matches.
            if (foundRange.location == NSNotFound) {
                foundRange.location = index;
            }
            index++;
            searchIndex++;
            if (searchIndex >= searchLength) {
                return foundRange;
            }
        }
        else {
            // Decrement to search backwards.
            if (foundRange.location == NSNotFound) {
                // Skip if first byte has been reached.
                if (index == 0) {
                    foundRange.location = NSNotFound;
                    return foundRange;
                }
                index--;
            }
            // Jump over the former found location
            // to avoid endless loop.
            else {
                index = index - 2;
            }
            searchIndex = 0;
            foundRange.location = NSNotFound;
        }
    }
    return foundRange;
}

- (NSString*)stringValueWithEncoding:(NSStringEncoding)encoding {
    return [[NSString alloc] initWithData:self encoding:encoding];
}

@end




// -----------------------------------------------------------------------------
// NSMutableData additions.
// -----------------------------------------------------------------------------


/**
 Extension of the NSMutableData class. 
 Data can be prepended in addition to the append function of the framework.
 @param Additions Category labeled Additions.
 @returns An initialized NSMutableData object or nil if the object could not be created.
 */
@implementation NSMutableData (Additions)

/**
    Inserts the data before the data of the object.
    @param data Data to be prepended.
 */
- (void)prepend:(NSData*)data {


    NSMutableData* concat = [NSMutableData dataWithData:data];
    [concat appendData:self];
    [self setData:concat];
}

@end

Answer 10

Je rencontre la même situation dans d’autres circonstances, et voici ma solution dans Swift 3. Supposons que le fichier texte soit utf8.

extension FileHandle {

    func enumerateLines(_ block: @escaping (String, UnsafeMutablePointer<Bool>) -> Void) {

        // find the end of file
        var offset = self.offsetInFile
        let eof = self.seekToEndOfFile()
        self.seek(toFileOffset: offset)
        let blockSize = 1024
        var buffer = Data()

        // process to the end of file
        while offset + UInt64(buffer.count) < eof {
            var found = false

            // make sure buffer contains at least one CR, LF or null
            while !found && offset + UInt64(buffer.count) < eof {
                let block = self.readData(ofLength: blockSize)
                buffer.append(block)
                for byte in block {
                    if [0x0d, 0x0a, 0x00].contains(byte) {
                        found = true ; break
                    }
                }
            }

            // retrieve lines within the buffer
            var index = 0
            var head = 0 // head of line
            var done = false
            buffer.enumerateBytes({ (pointer, count, stop) in
                while index < count {
                    // find a line terminator
                    if [0x0d, 0x0a, 0x00].contains(pointer[index]) {
                        let lineData = Data(pointer[head ..< index])
                        if let line = String(bytes: lineData, encoding: .utf8) {
                            block(line, &stop) // stop requested
                            if pointer[index] == 0x0d && index+1 < count && pointer[index+1] == 0x0a {
                                index += 2 ; head = index
                            }
                            else { index += 1 ; head = index }
                            if stop { done = true ; return } // end of enumerateLines
                        }
                        else { return } // end of enumerateLines
                    }
                    else { index += 1 }
                }
            })

            offset += UInt64(head)
            buffer.replaceSubrange(0 ..< head, with: Data())
            if done { // stop requested
                self.seek(toFileOffset: offset)
                return
            }
        }
    }

Voici l'usage:

    let fileURL = Bundle.main.url(forResource: "huge_file", withExtension: "txt")!
    let fileHandle = try! FileHandle(forReadingFrom: fileURL)

    fileHandle.enumerateLines { (line, stop) in
        if someCondition { stop.pointee = true }
        print(line)
    }
    /* let remaining = fileHandle.readDataToEndOfFile() */

https://Gist.github.com/codelynx/c1de603a85e7503fe9597d027e93f4de