1 files changed, 98 insertions, 0 deletions
diff --git a/adler32.c b/adler32.c
new file mode 100644
index 0000000..7a1a5e7
--- /dev/null
+++ b/adler32.c
@@ -0,0 +1,98 @@
+/*
+ * adler32.c (c) 2006 Bjorn Lindeijer
+ * License: GPL, v2 or later
+ *
+ * Calculates Adler-32 checksums for all files passed as argument.
+ *
+ *  Usage: adler32 [file]...
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+//#include <zlib.h>
+
+const uint32_t MOD_ADLER = 65521;
+
+uint32_t adler32(unsigned char *data, size_t len)
+/*
+    where data is the location of the data in physical memory and
+    len is the length of the data in bytes
+*/
+{
+    uint32_t a = 1, b = 0;
+    size_t index;
+
+    // Process each byte of the data in order
+    for (index = 0; index < len; ++index)
+    {
+        a = (a + data[index]) % MOD_ADLER;
+        b = (b + a) % MOD_ADLER;
+    }
+
+    return (b << 16) | a;
+}
+
+
+/**
+ * Calculates the Adler-32 checksum for the given file.
+ */
+unsigned long fadler32(FILE *file)
+{
+    // Obtain file size
+    fseek(file, 0, SEEK_END);
+    long fileSize = ftell(file);
+    rewind(file);
+
+    // Calculate Adler-32 checksum
+    unsigned char *buffer = (unsigned char*) malloc(fileSize);
+    fread(buffer, 1, fileSize, file);
+    //unsigned long adler = adler32(0L, Z_NULL, 0);
+    //adler = adler32(adler, (Bytef*) buffer, fileSize);
+    unsigned long adler = adler32(buffer, fileSize);
+    free(buffer);
+
+    return adler;
+}
+
+/**
+ * Prints out usage and exists.
+ */
+void print_usage()
+{
+    printf("Usage: adler32 mode [file]...\n");
+    exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+    int i;                            /**< Loops through arguments. */
+    if (argc < 2)
+    {
+        print_usage();
+    }
+    int mode = atoi(argv[1]);
+    for (i = 2; i < argc; ++i)
+    {
+        FILE *file = fopen(argv[i], "r");
+        if (!file)
+        {
+            printf("Error while opening '%s' for reading!\n", argv[i]);
+            exit(1);
+        }
+
+        unsigned long adler = fadler32(file);
+        switch (mode)
+        {
+            case 0:
+            default:
+                printf("%s %lx\n", argv[i], adler);
+                break;
+            case 1:
+                printf("%lx", adler);
+                break;
+        }
+        fclose(file);
+    }
+    return 0;
+}