Implement inet_pton for AF_INET6 (#583)

Author: G4Vi

libc/sock/inet_pton.c

@@ -24,17 +24,139 @@
 #include "libc/sysv/consts/inaddr.h"
 #include "libc/sysv/errfuns.h"
 
+static inline void add_set(unsigned __int128 *pResTemp, uint16_t *pCurrentSet,
+                           unsigned *pDigitsLeft) {
+  *pDigitsLeft -= *pDigitsLeft % 4;
+  *pResTemp = (*pResTemp << 16) | *pCurrentSet;
+  *pCurrentSet = 0;
+}
+
+static int inet_pton_inet6_impl(const char *src, uint8_t *dst) {
+  enum STATES {
+    COLON_OK = 1 << 0,
+    COLON_WAS = 1 << 1,
+    DIGIT_OK = 1 << 2,
+    COLON_OR_DIGIT = COLON_OK | DIGIT_OK,
+  };
+
+  unsigned __int128 res = 0;
+  unsigned __int128 resTemp = 0;
+  char c;
+  enum STATES state = COLON_OR_DIGIT;
+  unsigned digitsLeft = 32;
+  bool zeroFound = false;
+  uint16_t currentSet = 0;
+  while (c = *src++) {
+    if (digitsLeft == 0) {
+      return 0;
+    }
+
+    if (state & COLON_OK) {
+      if (c == ':') {
+        if (state & COLON_WAS) {
+          if (zeroFound) {
+            return 0;
+          }
+          res = resTemp << (4 * digitsLeft);
+          resTemp = 0;
+          digitsLeft -= 4;
+          zeroFound = true;
+          state = DIGIT_OK;
+        } else {
+          if (digitsLeft % 4) {
+            add_set(&resTemp, &currentSet, &digitsLeft);
+          } else if (digitsLeft == 32) {
+            state = COLON_OK;
+          } else {
+            state = COLON_OR_DIGIT;
+          }
+          state |= COLON_WAS;
+        }
+        continue;
+      }
+    }
+
+    if (state & DIGIT_OK) {
+      if ((c >= '0') && ((c < ':') || ((c >= 'A') && (c < 'G')) ||
+                         ((c >= 'a') && (c < 'g')))) {
+        state &= (~COLON_WAS);
+        uint8_t digit;
+        if (c < ':') {
+          digit = c - '0';
+        } else if (c < 'G') {
+          digit = c - 'A' + 10;
+        } else {
+          digit = c - 'a' + 10;
+        }
+        currentSet = (currentSet << 4) | digit;
+        digitsLeft--;
+        if (!(digitsLeft % 4)) {
+          state = COLON_OK;
+          add_set(&resTemp, &currentSet, &digitsLeft);
+        } else if ((state == DIGIT_OK) && (digitsLeft > 4)) {
+          state = COLON_OR_DIGIT;
+        }
+        continue;
+      } else if ((c == '.') && (digitsLeft >= 5) && (digitsLeft <= 27) &&
+                 (digitsLeft % 4)) {
+        uint8_t ipv4[4];
+        const unsigned digitsRead = 4 - digitsLeft % 4;
+        if (inet_pton(AF_INET, src - (1 + digitsRead), &ipv4) == 1) {
+          state &= (~COLON_WAS);
+          digitsLeft += digitsRead;
+          currentSet = (ipv4[0] << 8) | ipv4[1];
+          digitsLeft -= 4;
+          add_set(&resTemp, &currentSet, &digitsLeft);
+          currentSet = (ipv4[2] << 8) | ipv4[3];
+          digitsLeft -= 4;
+          add_set(&resTemp, &currentSet, &digitsLeft);
+          break;
+        }
+      }
+    }
+    return 0;
+  }
+  if (state & COLON_WAS) {
+    return 0;
+  } else if (digitsLeft % 4) {
+    add_set(&resTemp, &currentSet, &digitsLeft);
+  }
+  if (!zeroFound && (digitsLeft != 0)) {
+    return 0;
+  }
+
+  res |= resTemp;
+  dst[0] = res >> (15 * 8);
+  dst[1] = res >> (14 * 8);
+  dst[2] = res >> (13 * 8);
+  dst[3] = res >> (12 * 8);
+  dst[4] = res >> (11 * 8);
+  dst[5] = res >> (10 * 8);
+  dst[6] = res >> (9 * 8);
+  dst[7] = res >> (8 * 8);
+  dst[8] = res >> (7 * 8);
+  dst[9] = res >> (6 * 8);
+  dst[10] = res >> (5 * 8);
+  dst[11] = res >> (4 * 8);
+  dst[12] = res >> (3 * 8);
+  dst[13] = res >> (2 * 8);
+  dst[14] = res >> (1 * 8);
+  dst[15] = res >> (0 * 8);
+  return 1;
+}
+
 /**
  * Converts internet address string to binary.
  *
- * @param af can be AF_INET
+ * @param af can be AF_INET or AF_INET6
  * @param src is the ASCII-encoded address
  * @param dst is where the binary-encoded net-order address goes
  * @return 1 on success, 0 on src malformed, or -1 w/ errno
  */
 int inet_pton(int af, const char *src, void *dst) {
   uint8_t *p;
   int b, c, j;
+  if (af == AF_INET6) return inet_pton_inet6_impl(src, dst);
   if (af != AF_INET) return eafnosupport();
   j = 0;
   p = dst;