Как читать данные из NSFileHandle по строкам?

Question

У меня есть текстовый файл с данными, указанными

например.

PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV 
PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV 

Теперь я хочу читать данные по строкам. Это означает, что сначала я хочу прочитать

PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV 

а затем следующий оставшийся. У кого-нибудь есть идея?

Answer 1

Если ваш файл невелик, то метод @ mipadi, вероятно, будет в порядке. Однако, если ваш файл большой (> 1MB, возможно?), Тогда вы можете захотеть прочитать файл по очереди. Я написал класс один раз, чтобы сделать это, что я вставить здесь:

//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 

Затем, чтобы использовать это, вы могли бы сделать:

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

Или (для 10.6+ и прошивкой 4+) :

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

С Рождеством Христовым. :)

Answer 2

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

В API Cocoa отсутствуют встроенные языковые конструкции для чтения файла по строкам.

Answer 3

Я запустил GitHub project на основе исходного кода Dave DeLong. Вы можете улучшить код. К настоящему времени я могу читать файлы вперед и назад.

Answer 4

Я изменил FileReader к категории NSFileHandle, надеется, что это может помочь другому

@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 5

я узнал, что GitX использует читатель линии, а также.
Оформить заказ brotherbard's repository on GitHub или website of the Michael Stapelberg.

@Joe Yang
Nice! Я посмотрю в ближайшие дни.
Я был бы рад, если вы хотите forkmy repository on GitHub и пришлите мне запрос на вытягивание.

Answer 6

я переписал это, чтобы быть совместимой АРК:

// 
// 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 7

Вот метод, который я использовал для чтения индивидуальной линии от NSInputStream. Обратите внимание, что он оптимизирован для удобства чтения, а не для скорости. ;-)

- (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 8

Вы также можете проверить библиотеку CGIStream я создал для моего проекта сервера HTTP в https://github.com/xcvista/ohttpd2/tree/master/CGIStream. Вместо файловых дескрипторов этот код работает на NSInputStream. Это, по сути, клонирование Objective-C от System.IO.StreamReader и System.IO.StreamWriter от Microsoft .net framework.

Он будет работать не только с файлами, но и с сетевыми сокетами. Я использую его для обработки HTTP-протокола, который является тезкой префикса CGI.

Answer 9

Ответ на этот вопрос для LARGE Текстовые файлы не требуют пользовательской функции. Objective-C - это надмножество c и поэтому имеет c-методы для этого.

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); 
} 

Обратите внимание, что fgetln не сохранит символ новой строки. Кроме того, We +1 - длина str, потому что мы хотим создать пространство для завершения NULL.

Answer 10

Я столкнулся с подобной ситуацией с некоторыми другими обстоятельствами, и вот мое решение в Swift 3. Предполагая, что текстовым файлом является 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 
      } 
     } 
    } 

Здесь использование:

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