NSFileHandleから行ごとにデータを読み取る方法は？

Question

指定されたデータを含むテキストファイルがあります

例えば.

PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV
PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV

次に、データを1行ずつ読み取りたいと思います。つまり、まず読みたい

PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV

そして次に残ります。誰もが考えていますか？

Answer 1

ファイルが小さい場合は、おそらく@mipadiの方法で十分です。ただし、ファイルが大きい場合（1 MBを超える、おそらく？）、ファイルを1行ずつ読み取ることを検討してください。これを行うために一度クラスを書いたので、ここに貼り付けます。

//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

次に、これを使用するには、次のようにします。

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

または（10.6以降およびiOS 4以降）：

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

メリークリスマス。 :)

Answer 2

私はこれをARCに準拠するように書き直しました：

//
//  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

GitHubプロジェクト のソースコードに基づいて Dave DeLong を開始しました。コードの改善を歓迎します。今では、ファイルを前後に読むことができます。

Answer 4

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

Cocoaには、ファイルを1行ずつ読み取るためのAPIや組み込みの言語構造はありません。

Answer 5

[〜＃〜] large [〜＃〜]テキストファイルに対するこの質問への回答には、カスタム関数は必要ありません。 Objective-Cはcのスーパーセットであるため、これを行うcメソッドがあります。

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);
}

Fgetlnは改行文字を保持しないことに注意してください。また、NULL終了用のスペースを確保するため、strの長さを+1します。

Answer 6

NSInputStreamから個々の行を読み取るために使用したメソッドを次に示します。速度ではなく読みやすさのために最適化されていることに注意してください。 ;-)

- (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 7

GitX もラインリーダーを使用していることがわかりました。
GitHubのブラザーバードのリポジトリ または Michael StapelbergのWebサイト をチェックアウトします。

@ Joe Yang
いいね！私は次の日を詳しく見ていきます。
forkGitHub上のリポジトリ およびプルリクエストを送ってください。

Answer 8

https://github.com/xcvista/ohttpd2/tree/master/CGIStream で、HTTPサーバープロジェクト用に作成したCGIStreamライブラリを確認することもできます。ファイル記述子の代わりに、このコードはNSInputStreamで動作します。本質的には、Microsoftの.netフレームワークからのSystem.IO.StreamReaderおよびSystem.IO.StreamWriterのObjective-Cクローンです。

ファイルだけでなく、ネットワークソケットでも動作します。これを使用して、CGIプレフィックスの同名であるHTTPプロトコルを処理します。

Answer 9

他のいくつかの状況でも同様の状況に陥ります。ここで、Swift 3.テキストファイルをutf8と仮定します。

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
            }
        }
    }

使用方法は次のとおりです。

    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

Answer 10

FileReaderをNSFileHandleカテゴリに変更しました。他の人に役立つことを願っています

@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