7.0 refactor

src/base64.c

@@ -0,0 +1,104 @@
+#include <string.h>
+
+static int mg_b64idx(int c) {
+  if (c < 26) {
+    return c + 'A';
+  } else if (c < 52) {
+    return c - 26 + 'a';
+  } else if (c < 62) {
+    return c - 52 + '0';
+  } else {
+    return c == 62 ? '+' : '/';
+  }
+}
+
+static int mg_b64rev(int c) {
+  if (c >= 'A' && c <= 'Z') {
+    return c - 'A';
+  } else if (c >= 'a' && c <= 'z') {
+    return c + 26 - 'a';
+  } else if (c >= '0' && c <= '9') {
+    return c + 52 - '0';
+  } else if (c == '+') {
+    return 62;
+  } else if (c == '/') {
+    return 63;
+  } else if (c == '=') {
+    return 64;
+  } else {
+    return -1;
+  }
+}
+
+int mg_base64_update(unsigned char ch, char *to, int n) {
+  unsigned char rem = (n & 3) % 3;
+  if (rem == 0) {
+    to[n] = mg_b64idx(ch >> 2);
+    to[++n] = (ch & 3) << 4;
+  } else if (rem == 1) {
+    to[n] = mg_b64idx(to[n] | (ch >> 4));
+    to[++n] = (ch & 15) << 2;
+  } else {
+    to[n] = mg_b64idx(to[n] | (ch >> 6));
+    to[++n] = mg_b64idx(ch & 63);
+    n++;
+  }
+  return n;
+}
+
+int mg_base64_final(char *to, int n) {
+  int saved = n;
+  // printf("---[%.*s]\n", n, to);
+  if (n & 3) n = mg_base64_update(0, to, n);
+  if ((saved & 3) == 2) n--;
+  // printf("    %d[%.*s]\n", n, n, to);
+  while (n & 3) to[n++] = '=';
+  to[n] = '\0';
+  return n;
+}
+
+int mg_base64_encode(const unsigned char *p, int n, char *to) {
+#if 0
+  char buf[4];
+  int i, j, len = 0;
+  for (i = 0; i < n; i += 3) {
+    int a = p[i], b = i + 1 < n ? p[i + 1] : 0, c = i + 2 < n ? p[i + 2] : 0;
+    buf[0] = mg_b64idx(a >> 2);
+    buf[1] = mg_b64idx((a & 3) << 4 | (b >> 4));
+    buf[2] = mg_b64idx((b & 15) << 2 | (c >> 6));
+    buf[3] = mg_b64idx(c & 63);
+    j = 0;
+    if (i + 1 >= n) buf[2] = '=', j++;
+    if (i + 2 >= n) buf[3] = '=', j++;
+    memcpy(to + len, buf, sizeof(buf));
+    len += sizeof(buf);
+  }
+  to[len] = '\0';
+  printf("%d[%.*s] -> %d[%.*s]\n", n, n, p, len, len, to);
+  return len;
+#else
+  int i, len = 0;
+  for (i = 0; i < n; i++) len = mg_base64_update(p[i], to, len);
+  len = mg_base64_final(to, len);
+  // printf("%d[%.*s] -> %d[%.*s]\n", n, n, p, len, len, to);
+  return len;
+#endif
+}
+
+int mg_base64_decode(const char *src, int n, char *dst) {
+  const char *end = src + n;
+  int len = 0;
+  while (src + 3 < end) {
+    int a = mg_b64rev(src[0]), b = mg_b64rev(src[1]), c = mg_b64rev(src[2]),
+        d = mg_b64rev(src[3]);
+    if (a == 64 || a < 0 || b == 64 || b < 0 || c < 0 || d < 0) return 0;
+    dst[len++] = (a << 2) | (b >> 4);
+    if (src[2] != '=') {
+      dst[len++] = (b << 4) | (c >> 2);
+      if (src[3] != '=') dst[len++] = (c << 6) | d;
+    }
+    src += 4;
+  }
+  dst[len] = '\0';
+  return len;
+}