kulp · August 17, 2015 17:33 · Aug 17, 2015
diff --git a/sha1.c b/sha1.c
@@ -0,0 +1,101 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <limits.h>
+
+static inline uint32_t rol(uint32_t x, unsigned char y)
+{
+    return (x << y) | ((x >> (32 - y)) & ~(-1 << y));
+}
+
+static void chunk(uint32_t h[5], unsigned char *ptr)
+{
+    uint32_t w[80];
+
+    for (int i = 0; i < 16; i++)
+        w[i] = (ptr[i * 4 + 0] << 24)
+             | (ptr[i * 4 + 1] << 16)
+             | (ptr[i * 4 + 2] <<  8)
+             | (ptr[i * 4 + 3] <<  0);
+
+    for (int i = 16; i < 80; i++)
+        w[i] = rol(w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16], 1);
+
+    uint32_t a = h[0],
+             b = h[1],
+             c = h[2],
+             d = h[3],
+             e = h[4];
+
+    static const uint32_t k[] =
+        { 0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6 };
+
+    for (int i = 0; i < 80; i++) {
+        uint32_t f =    (i < 20) ?  (b & c) | (~b & d)          :
+                        (i < 40) ?  b ^ c ^ d                   :
+                        (i < 60) ?  (b & c) | (b & d) | (c & d) :
+                                    b ^ c ^ d;
+
+        uint32_t temp = rol(a, 5) + f + e + k[i / 20] + w[i];
+        e = d;
+        d = c;
+        c = rol(b, 30);
+        b = a;
+        a = temp;
+    }
+
+    h[0] += a;
+    h[1] += b;
+    h[2] += c;
+    h[3] += d;
+    h[4] += e;
+}
+
+void process_stream(FILE *in, const char *fname)
+{
+    uint32_t h[] =
+        { 0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0 };
+
+    const int chunkbytes = 512 / CHAR_BIT;
+    unsigned char buf[chunkbytes * 2];
+    size_t end = 0, pos = 0;
+    while (!feof(in) && !ferror(in)) {
+        end += fread(buf, 1, chunkbytes, in);
+
+        if (end - pos >= chunkbytes) {
+            chunk(h, buf);
+            pos += chunkbytes;
+        }
+    }
+
+    if (ferror(in)) {
+        perror("sha1");
+        return;
+    }
+
+    // handle last chunk which is necessarily < 512 bits long
+    uint64_t ml = end * CHAR_BIT;
+    buf[end++ - pos] = 1 << (CHAR_BIT - 1);
+    while ((end - pos) % 64 != 56)
+        buf[end++ - pos] = 0x00;
+
+    size_t idx = end - pos;
+    for (int i = 0; i < 64 / CHAR_BIT; i++)
+        buf[idx + i] = (ml >> ((7 - i) * CHAR_BIT)) & 0xff;
+
+    for (size_t off = 0; off < idx; off += 64)
+        chunk(h, &buf[off]);
+
+    printf("%08x%08x%08x%08x%08x  %s\n", h[0], h[1], h[2], h[3], h[4], fname);
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc <= 1) {
+        process_stream(stdin, "-");
+    } else for (int i = 1; i < argc; i++) {
+        FILE *in = fopen(argv[i], "rb");
+        process_stream(in, argv[i]);
+        fclose(in);
+    }
+}
+