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enumerate lines from FileHandle (NSFileHandle) in swift3 – good for enumerating huge text file line by line
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| // | |
| // FileHandle+Z.swift | |
| // ZKit | |
| // | |
| // The MIT License (MIT) | |
| // | |
| // Copyright (c) 2016 Electricwoods LLC, Kaz Yoshikawa. | |
| // | |
| // Permission is hereby granted, free of charge, to any person obtaining a copy | |
| // of this software and associated documentation files (the "Software"), to deal | |
| // in the Software without restriction, including without limitation the rights | |
| // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
| // copies of the Software, and to permit persons to whom the Software is | |
| // furnished to do so, subject to the following conditions: | |
| // | |
| // The above copyright notice and this permission notice shall be included in | |
| // all copies or substantial portions of the Software. | |
| // | |
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
| // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
| // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, | |
| // WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
| // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
| // THE SOFTWARE. | |
| // | |
| import Foundation | |
| 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) | |
| 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 } // stop requested | |
| } | |
| 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 | |
| } | |
| } | |
| } | |
| } |
Author
codelynx
commented
Nov 22, 2016
•
How does the property 'count' get initialized in the block called by enumerateBytes? When I run your code sample the while loop on line 61 never gets executed due to 'count' property always being equal to zero. I had to modify 'count' to 'buffer.count' on lines 61 and 67 in order for the while loop to be executed, but this does not seem like appropriate fix. Thanks!
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