Initial commit.

main.c

@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2012 Natalia Portillo.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define BLOCK_SIZE 65536
+
+void show_usage() { printf("Usage: dd-diff <input_path> <output_path> [block_size]\n"); }
+
+int main(int argc, char** argv)
+{
+    int     block_size = BLOCK_SIZE;
+    ssize_t in_read, out_read, to_process, total_written = 0;
+    int     fd_in, fd_out;
+    char *  in_buf, *out_buf;
+    int     i, dif;
+    off_t   last_pos, current_pos;
+
+    printf("dd-diff A DD that only writes changed blocks.\n");
+    printf("Copyright (C) 2022 Natalia Portillo\n");
+
+    if(argc != 3 && argc != 4)
+    {
+        show_usage();
+        return 1;
+    }
+
+    if(argc == 4)
+    {
+        block_size = atoi(argv[3]);
+        if(block_size == 0) block_size = BLOCK_SIZE;
+    }
+
+    in_buf = malloc(block_size);
+
+    if(in_buf == NULL)
+    {
+        printf("Error: could not allocate memory.\n");
+        return 1;
+    }
+
+    out_buf = malloc(block_size);
+
+    if(out_buf == NULL)
+    {
+        printf("Error: could not allocate memory.\n");
+        free(out_buf);
+        return 1;
+    }
+
+    fd_in = open(argv[1], O_RDONLY);
+
+    if(fd_in < 0)
+    {
+        printf("Error opening input file.\n");
+        free(in_buf);
+        free(out_buf);
+        return 1;
+    }
+
+    fd_out = open(argv[2], O_RDWR);
+
+    if(fd_out < 0)
+    {
+        printf("Error opening output file.\n");
+        free(in_buf);
+        free(out_buf);
+        return 1;
+    }
+
+    last_pos = lseek(fd_in, 0, SEEK_END);
+    lseek(fd_in, 0, SEEK_SET);
+
+    in_read = read(fd_in, in_buf, block_size);
+
+    while(in_read > 0)
+    {
+        current_pos = lseek(fd_in, 0, SEEK_CUR);
+        printf("Processing position %ld of %ld (%f%%)\n",
+               current_pos,
+               last_pos,
+               ((float)current_pos * 100.0) / (float)last_pos);
+
+        out_read = read(fd_out, out_buf, block_size);
+
+        to_process = in_read;
+        if(out_read < to_process) to_process = out_read;
+
+        dif = false;
+        for(i = 0; i < to_process; i++)
+        {
+            if(in_buf[i] != out_buf[i])
+            {
+                dif = true;
+                break;
+            }
+        }
+
+        if(dif)
+        {
+            lseek(fd_in, -in_read, SEEK_CUR);
+            lseek(fd_out, -out_read, SEEK_CUR);
+            total_written += write(fd_out, in_buf, to_process);
+        }
+
+        in_read = read(fd_in, in_buf, block_size);
+    }
+
+    close(fd_in);
+    close(fd_out);
+    free(in_buf);
+    free(out_buf);
+
+    return 0;
+}