Wie man Daten von NSFileHandle Zeile für Zeile lesen?
https://stackoverflow.com/questions/3707427
-
02-10-2019 - |
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Ich habe eine Textdatei Daten, wie angegeben
z.
PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV
PUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV
Jetzt möchte ich Daten Zeile für Zeile lesen. Das bedeutet zunächst möchte ich
lesenPUFGUjVRallYZDNaazFtVjVObU1zWm5ZcUJUYU5ORk4zbGthNHNDVUdSMlFVQmpSVEoxUUNSallYaFhkanBITXBGR1NTQnpZRTltZE1OalVzSkdXQ0Z6WXR0V2RpTmpTdXgwTWs5V1lZSkZiWjFXT29OV2JSVlhaSTUwYUpwR040UUZXTzVHVXFoWFVRcFdWNHdVTUJ0Q1VHSmxXVlJVTlJCMVE1VTFWV
und dann weiter zu bleiben. Hat jemand eine Idee ??
Lösung
Wenn die Datei klein ist, dann @ mipadi Methode wird wahrscheinlich nur in Ordnung sein. Allerdings, wenn Ihre Datei groß ist (> 1 MB, vielleicht?), Dann können Sie die Datei Zeile-für-Zeile lesen zu betrachten. Ich schrieb eine Klasse einmal das zu tun, was ich hier einfügen:
//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
Dann ist dieses zu verwenden, würden Sie tun:
DDFileReader * reader = [[DDFileReader alloc] initWithFilePath:pathToMyFile];
NSString * line = nil;
while ((line = [reader readLine])) {
NSLog(@"read line: %@", line);
}
[reader release];
oder (für 10.6+ und iOS 4 +):
DDFileReader * reader = [[DDFileReader alloc] initWithFilePath:pathToMyFile];
[reader enumerateLinesUsingBlock:^(NSString * line, BOOL * stop) {
NSLog(@"read line: %@", line);
}];
[reader release];
Frohe Weihnachten. :)
Andere Tipps
ich diese neu geschrieben ARC kompatibel zu sein:
//
// 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
begann ich ein GitHub Projekt auf dem Quellcode basiert von Dave DeLong . Sie sind willkommen, den Code zu verbessern. Inzwischen kann ich Dateien vorwärts lesen und zurück.
NSString *fh = [NSString stringWithContentsOfFile:filePath encoding:fileEncoding error:NULL];
for (NSString *line in [fh componentsSeparatedByString:@"\n"]) {
// Do something with the line
}
Es gibt keine API in Cocoa oder eingebaute Sprachkonstrukten für eine Datei Zeile für Zeile zu lesen.
Die Antwort auf diese Frage für LARGE Textdateien benötigen keine eigene Funktion. Objective-C ist eine Obermenge von c, und hat daher die c-Methoden zu tun, nur diese.
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);
}
Beachten Sie, dass fgetln nicht Ihre Newline-Zeichen halten. Auch wir 1 die Länge des str, weil wir wollen, um Platz für die NULL-Terminierung machen.
Dies ist eine Methode, die ich für das Lesen eines einzelnen Linie von einem NSInputStream verwendet. Beachten Sie, dass es für die Lesbarkeit und nicht auf Geschwindigkeit optimiert ist. ; -)
- (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];
Ich fand heraus, dass GitX verwendet eine Linie Leser auch.
Kasse des brotherbard Repository auf GitHub oder das Website des Michael Stapelberg.
@ Joe Yang
Nett! Ich werde in den nächsten Tagen genaues hinsehen.
Ich würde mich freuen, wenn Sie auf wollen Gabel mein Repository auf GitHub und mir eine Pull-Anforderung senden .
Ich habe die Filereader zu einer NSFileHandle Kategorie geändert, hoffen, dass es anderen helfen könnte
@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
Sie können auch die CGIStream Bibliothek überprüfen, die für eine HTTP-Server-Projekt erstellt unter https: //github.com/xcvista/ohttpd2/tree/master/CGIStream . Anstelle von Datei-Deskriptoren, arbeitet dieser Code auf NSInputStream. Es ist im Wesentlichen ein Objective-C-Klon von System.IO.StreamReader und System.IO.StreamWriter von Microsoft .NET Framework.
Es wird nicht nur mit Dateien arbeiten, sondern auch Netzwerk-Sockets. Ich benutze es HTTP-Protokoll zu handhaben, die der Namensgeber des CGI-Präfix ist.
Ich laufe in die ähnliche Situation mit einigen anderen Umständen, und hier ist meine Lösung in Swift 3. Textdatei Unter der Annahme, UTF-8 sein.
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
}
}
}
Hier ist die Nutzung:
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
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