Changeset 5ee9692 in mainline for uspace/lib/posix/stdlib/strtold.c

Timestamp:

2011-06-19T13:23:54Z (14 years ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

918e236f

Parents:

63fc519

Message:

strtold(): fix problem with leading zeros and exponent overflow

File:

• uspace/lib/posix/stdlib/strtold.c (modified) (9 diffs)

uspace/lib/posix/stdlib/strtold.c

@@ -53 +53 @@
 #endif
 
-// TODO: documentation
+// TODO: clean up, documentation
 
 // FIXME: ensure it builds and works on all platforms
@@ -238 +238 @@
         /* digits before decimal point */
         while (isdigit(str[i])) {
-                if (parsed_digits < PARSE_DECIMAL_DIGS) {
+                if (parsed_digits == 0 && str[i] == '0') {
+                        /* Nothing, just skip leading zeros. */
+                } else if (parsed_digits < PARSE_DECIMAL_DIGS) {
                         significand *= DEC_BASE;
                         significand += str[i] - '0';
@@ -254 +256 @@
                 /* digits after decimal point */
                 while (isdigit(str[i])) {
-                        if (parsed_digits < PARSE_DECIMAL_DIGS) {
+                        if (parsed_digits == 0 && str[i] == '0') {
+                                /* Skip leading zeros and decrement exponent. */
+                                exponent--;
+                        } else if (parsed_digits < PARSE_DECIMAL_DIGS) {
                                 significand *= DEC_BASE;
                                 significand += str[i] - '0';
@@ -282 +287 @@
                 }
                 
-                while (isdigit(str[i])) {
+                while (isdigit(str[i]) && exp < 65536) {
                         exp *= DEC_BASE;
                         exp += str[i] - '0';
@@ -306 +311 @@
 }
 
-static inline int hex_value(char ch) {
+static inline int hex_value(char ch)
+{
         if (ch <= '9') {
                 return ch - '0';
@@ -312 +318 @@
                 return 10 + tolower(ch) - 'a';
         }
+}
+
+/**
+ * @param val Integer value.
+ * @return How many leading zero bits there are. (Maximum is 3)
+ */
+static inline int leading_zeros(uint64_t val)
+{
+        for (int i = 3; i > 0; --i) {
+                if ((val >> (64 - i)) == 0) {
+                        return i;
+                }
+        }
+        
+        return 0;
 }
 
@@ -345 +366 @@
         /* digits before decimal point */
         while (posix_isxdigit(str[i])) {
-                if (parsed_digits < PARSE_HEX_DIGS) {
+                if (parsed_digits == 0 && str[i] == '0') {
+                        /* Nothing, just skip leading zeros. */
+                } else if (parsed_digits < PARSE_HEX_DIGS) {
                         significand *= HEX_BASE;
                         significand += hex_value(str[i]);
                         parsed_digits++;
+                } else if (parsed_digits == PARSE_HEX_DIGS) {
+                        /* The first digit may have had leading zeros,
+                         * so we need to parse one more digit and shift
+                         * the value accordingly.
+                         */
+                        
+                        int zeros = leading_zeros(significand);
+                        significand = (significand << zeros) |
+                            (hex_value(str[i]) >> (4 - zeros));
+                        
+                        exponent += (4 - zeros);
+                        parsed_digits++;
                 } else {
                         exponent += 4;
@@ -361 +396 @@
                 /* digits after decimal point */
                 while (posix_isxdigit(str[i])) {
-                        if (parsed_digits < PARSE_HEX_DIGS) {
+                        if (parsed_digits == 0 && str[i] == '0') {
+                                /* Skip leading zeros and decrement exponent. */
+                                exponent -= 4;
+                        } else if (parsed_digits < PARSE_HEX_DIGS) {
                                 significand *= HEX_BASE;
                                 significand += hex_value(str[i]);
                                 exponent -= 4;
+                                parsed_digits++;
+                        } else if (parsed_digits == PARSE_HEX_DIGS) {
+                                /* The first digit may have had leading zeros,
+                                 * so we need to parse one more digit and shift
+                                 * the value accordingly.
+                                 */
+                                
+                                int zeros = leading_zeros(significand);
+                                significand = (significand << zeros) |
+                                    (hex_value(str[i]) >> (4 - zeros));
+                                
+                                exponent -= zeros;
                                 parsed_digits++;
                         } else {
@@ -389 +439 @@
                 }
                 
-                while (isdigit(str[i])) {
+                while (isdigit(str[i]) && exp < 65536) {
                         exp *= DEC_BASE;
                         exp += str[i] - '0';