[libc-commits] [libc] [libc] Add max length argument to decimal to float (PR #84091)

[via libc-commits]

================
@@ -38,60 +42,75 @@ LIBC_INLINE int b36_char_to_int(char input) {
 
 // checks if the next 3 characters of the string pointer are the start of a
 // hexadecimal number. Does not advance the string pointer.
-LIBC_INLINE bool is_hex_start(const char *__restrict src) {
+LIBC_INLINE bool
+is_hex_start(const char *__restrict src,
+             size_t src_len = cpp::numeric_limits<size_t>::max()) {
+  if (src_len < 3)
+    return false;
   return *src == '0' && (*(src + 1) | 32) == 'x' && isalnum(*(src + 2)) &&
          b36_char_to_int(*(src + 2)) < 16;
 }
 
+struct BaseAndLen {
+  int base;
+  size_t len;
+};
+
 // Takes the address of the string pointer and parses the base from the start of
 // it. This function will advance |src| to the first valid digit in the inferred
 // base.
-LIBC_INLINE int infer_base(const char *__restrict *__restrict src) {
+LIBC_INLINE BaseAndLen infer_base(const char *__restrict src, size_t src_len) {
   // A hexadecimal number is defined as "the prefix 0x or 0X followed by a
   // sequence of the decimal digits and the letters a (or A) through f (or F)
   // with values 10 through 15 respectively." (C standard 6.4.4.1)
-  if (is_hex_start(*src)) {
-    (*src) += 2;
-    return 16;
+  if (is_hex_start(src, src_len)) {
+    return {16, 2};
   } // An octal number is defined as "the prefix 0 optionally followed by a
     // sequence of the digits 0 through 7 only" (C standard 6.4.4.1) and so any
     // number that starts with 0, including just 0, is an octal number.
-  else if (**src == '0') {
-    return 8;
+  else if (src_len > 0 && src[0] == '0') {
+    return {8, 0};
   } // A decimal number is defined as beginning "with a nonzero digit and
     // consist[ing] of a sequence of decimal digits." (C standard 6.4.4.1)
   else {
-    return 10;
+    return {10, 0};
----------------
lntue wrote:

Use early return for this function:
```
if (is_hex_start(src, src_len))
  return ...;
if (...)
   return ...;
return ...;
```

https://github.com/llvm/llvm-project/pull/84091