Strip EXIF metadata from a JPEG

JpegExifStripper.m

//
//  Created by Kevin Wojniak on 2014/9/23.
//  Copyright (c) 2014 Kevin Wojniak. All rights reserved.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    const char *inputFile = argv[1];
    const char *outputFile = argv[2];
    
    FILE *inFile = fopen(inputFile, "rb");
    if (!inFile) {
        NSLog(@"Can't open %s", inputFile);
        return 0;
    }
    
    FILE *outFile = fopen(outputFile, "w");
    if (!outFile) {
        (void)fclose(inFile);
        NSLog(@"Can't open %@", outFile);
        return 0;
    }
    
    NSMutableData *data = [NSMutableData data];
    
    unsigned num_markers = 0;
    bool gotEndOfImage = false;
    for (;;) {
        size_t bytes_read;
        uint16_t raw_marker;
        bytes_read = fread(&raw_marker, 1, sizeof(raw_marker), inFile);
        if (bytes_read == 0) {
            // done
            break;
        }
        if (bytes_read != sizeof(raw_marker)) {
            NSLog(@"Can't read marker: %u", (unsigned)bytes_read);
            break;
        }
        uint16_t marker = NSSwapBigShortToHost(raw_marker);
        ++num_markers;
        
        if (num_markers == 1 && marker != 0xFFD8) {
            NSLog(@"Invalid starting marker %04X", marker);
            break;
        }
        
        if ((marker >> 8) != 0xFF) {
            NSLog(@"Invalid marker %04X", marker);
            break;
        }
        
        uint64_t len = 0;
        bool marker_has_length = true;

        if (marker == 0xFFD8 /* Start of Image */) {
            if (num_markers != 1) {
                NSLog(@"Got Start of Image marker at invalid location.");
                break;
            }
            marker_has_length = false;
        } else if (marker == 0xFFD9 /* End of Image */) {
            gotEndOfImage = true;
            marker_has_length = false;
        } else if (marker == 0xFFDA /* Start of Scan */) {
            int chr;
            while ((chr = fgetc(inFile)) != EOF) {
                ++len;
                if (chr == 0xFF) {
                    int nextchr = fgetc(inFile);
                    if (nextchr == 0 || (((nextchr & 0xFF) >= 0xD0) && ((nextchr & 0xFF) <= 0xD7))) {
                        ungetc(nextchr, inFile);
                        continue;
                    }
                    ++len;
                    if (fseek(inFile, -(long)len, SEEK_CUR) != 0) {
                        NSLog(@"Can't seek");
                    }
                    marker_has_length = false;
                    len -= sizeof(marker);
                    break;
                }
            }
        }
        
        NSLog(@"%04X", marker);

        uint16_t raw_len = 0;
        if (marker_has_length) {
            if (fread(&raw_len, 1, sizeof(raw_len), inFile) != sizeof(raw_len)) {
                NSLog(@"Can't read marker length.");
                break;
            }
            len = NSSwapBigShortToHost(raw_len);
            NSLog(@"  = %llu", len);
            len -= sizeof(raw_len);
        } else {
            NSLog(@"  ? %llu", len);
        }
        
        if (len > 0) {
            data.length = len;
            if (fread(data.mutableBytes, 1, len, inFile) != len) {
                NSLog(@"Can't read %04X's data of length %llu", marker, len);
                break;
            }
        }
        
        if (((marker & 0xFF) >= 0xE0) && ((marker & 0xFF) <= 0xEE)) {
            NSLog(@"  Skipping");
            continue;
        }

        if (fwrite(&raw_marker, 1, sizeof(raw_marker), outFile) != sizeof(raw_marker)) {
            NSLog(@"Can't write marker");
            break;
        }
        if (marker_has_length) {
            if (fwrite(&raw_len, 1, sizeof(raw_len), outFile) != sizeof(raw_len)) {
                NSLog(@"Can't write length");
                break;
            }
        }
        if (len > 0 && fwrite(data.bytes, 1, data.length, outFile) != data.length) {
            NSLog(@"Can't write data");
            break;
        }
    }
    
    (void)fclose(outFile);
    (void)fclose(inFile);
    
    if (!gotEndOfImage) {
        NSLog(@"Didn't get end of image marker");
    }
    
    return 0;
}