From ddf8881308b27f308aa456bef3e4833bc0383413 Mon Sep 17 00:00:00 2001 From: Serge Aleynikov Date: Fri, 25 Jan 2013 15:58:41 -0500 Subject: float_to_list/2 changed rounding and cosmetic cleanup Changed rouding to round half-way up instead of down. Cosmetic cleanup and error handling of additional edge cases. --- erts/emulator/sys/common/erl_sys_common_misc.c | 195 ++++++++++++++----------- 1 file changed, 111 insertions(+), 84 deletions(-) (limited to 'erts/emulator/sys/common/erl_sys_common_misc.c') diff --git a/erts/emulator/sys/common/erl_sys_common_misc.c b/erts/emulator/sys/common/erl_sys_common_misc.c index 1bf5fa89f4..5523b6fc0b 100644 --- a/erts/emulator/sys/common/erl_sys_common_misc.c +++ b/erts/emulator/sys/common/erl_sys_common_misc.c @@ -107,9 +107,9 @@ int erts_get_native_filename_encoding(void) } /* For internal use by sys_double_to_chars_fast() */ -static char* float_first_trailing_zero(char* p) +static char* find_first_trailing_zero(char* p) { - for (--p; *p == '0' && *(p-1) == '0'; --p); + for (; *(p-1) == '0'; --p); if (*(p-1) == '.') ++p; return p; } @@ -120,34 +120,83 @@ sys_double_to_chars(double fp, char *buffer, size_t buffer_size) return sys_double_to_chars_ext(fp, buffer, buffer_size, SYS_DEFAULT_FLOAT_DECIMALS); } +/* Convert float to string using fixed point notation. + * decimals must be >= 0 + * if compact != 0, the trailing 0's will be truncated + */ int -sys_double_to_chars_fast(double f, char *outbuf, int maxlen, int decimals, int compact) +sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals, int compact) { - enum { - FRAC_SIZE = 52 - , EXP_SIZE = 11 - , EXP_MASK = (1ll << EXP_SIZE) - 1 - , FRAC_MASK = (1ll << FRAC_SIZE) - 1 - , FRAC_MASK2 = (1ll << (FRAC_SIZE + 1)) - 1 - , MAX_FLOAT = 1ll << (FRAC_SIZE+1) + /* Note that some C compilers don't support "static const double" propagation into + * arrays so we use a define */ + #define SYS_DOUBLE_RND_CONST 0.55555555555555555 + + static const double cs_sys_double_pow10[] = { + SYS_DOUBLE_RND_CONST / 1ll, + SYS_DOUBLE_RND_CONST / 10ll, + SYS_DOUBLE_RND_CONST / 100ll, + SYS_DOUBLE_RND_CONST / 1000ll, + SYS_DOUBLE_RND_CONST / 10000ll, + SYS_DOUBLE_RND_CONST / 100000ll, + SYS_DOUBLE_RND_CONST / 1000000ll, + SYS_DOUBLE_RND_CONST / 10000000ll, + SYS_DOUBLE_RND_CONST / 100000000ll, + SYS_DOUBLE_RND_CONST / 1000000000ll, + SYS_DOUBLE_RND_CONST / 10000000000ll, + SYS_DOUBLE_RND_CONST / 100000000000ll, + SYS_DOUBLE_RND_CONST / 1000000000000ll, + SYS_DOUBLE_RND_CONST / 10000000000000ll, + SYS_DOUBLE_RND_CONST / 100000000000000ll, + SYS_DOUBLE_RND_CONST / 1000000000000000ll, + SYS_DOUBLE_RND_CONST / 10000000000000000ll, + SYS_DOUBLE_RND_CONST / 100000000000000000ll, + SYS_DOUBLE_RND_CONST / 1000000000000000000ll }; - long long mantissa, int_part, int_part2, frac_part; + static const int FRAC_SIZE = 52; + static const int EXP_SIZE = 11; + static const int EXP_MASK = (1ll << EXP_SIZE) - 1; + static const int MAX_DECIMALS = sizeof(cs_sys_double_pow10) / sizeof(cs_sys_double_pow10[0]); + + static const long long FRAC_MASK = (1ll << FRAC_SIZE) - 1; + static const long long FRAC_MASK2 = (1ll << (FRAC_SIZE + 1)) - 1; + static const long long MAX_FLOAT = 1ll << (FRAC_SIZE+1); + + long long mantissa, int_part = 0, frac_part = 0; short exp; - int sign, i, n, m, max; - double absf; + int max; + int neg; + double fr; union { long long L; double F; } x; - char c, *p = outbuf; - int digit, roundup; + char *p = buffer; - x.F = f; + if (decimals < 0) + return -1; + + /* Round the number to given decimal places. The number of 5's in the + * SYS_DOUBLE_RND_CONST constant is chosen such that adding any more 5's doesn't + * change the double precision of the number, i.e.: + * 1> term_to_binary(0.55555555555555555, [{minor_version, 1}]). + * <<131,70,63,225,199,28,113,199,28,114>> + * 2> term_to_binary(0.5555555555555555555, [{minor_version, 1}]). + * <<131,70,63,225,199,28,113,199,28,114>> + */ + if (f >= 0) { + neg = 0; + fr = decimals < MAX_DECIMALS ? (f + cs_sys_double_pow10[decimals]) : f; + x.F = fr; + } else { + neg = 1; + fr = decimals < MAX_DECIMALS ? (f - cs_sys_double_pow10[decimals]) : f; + x.F = -fr; + } exp = (x.L >> FRAC_SIZE) & EXP_MASK; mantissa = x.L & FRAC_MASK; - sign = x.L >= 0 ? 1 : -1; + if (exp == EXP_MASK) { if (mantissa == 0) { - if (sign == -1) + if (neg) *p++ = '-'; *p++ = 'i'; *p++ = 'n'; @@ -158,101 +207,79 @@ sys_double_to_chars_fast(double f, char *outbuf, int maxlen, int decimals, int c *p++ = 'n'; } *p = '\0'; - return p - outbuf; + return p - buffer; } exp -= EXP_MASK >> 1; mantissa |= (1ll << FRAC_SIZE); - frac_part = 0; - int_part = 0; - absf = f * sign; - - /* Don't bother with optimizing too large numbers and decimals */ - if (absf > MAX_FLOAT || decimals > maxlen-17) { - int len = erts_snprintf(outbuf, maxlen, "%.*f", decimals, f); - if (len >= maxlen) + + /* Don't bother with optimizing too large numbers or too large precision */ + if (x.F > MAX_FLOAT || decimals >= MAX_DECIMALS) { + int len = erts_snprintf(buffer, buffer_size, "%.*f", decimals, f); + char* p = buffer + len; + if (len >= buffer_size) return -1; - p = outbuf + len; /* Delete trailing zeroes */ if (compact) - p = float_first_trailing_zero(outbuf + len); + p = find_first_trailing_zero(p); *p = '\0'; - return p - outbuf; - } - - if (exp >= FRAC_SIZE) + return p - buffer; + } else if (exp >= FRAC_SIZE) { int_part = mantissa << (exp - FRAC_SIZE); - else if (exp >= 0) { + } else if (exp >= 0) { int_part = mantissa >> (FRAC_SIZE - exp); frac_part = (mantissa << (exp + 1)) & FRAC_MASK2; - } - else /* if (exp < 0) */ + } else /* if (exp < 0) */ { frac_part = (mantissa & FRAC_MASK2) >> -(exp + 1); + } - if (int_part == 0) { - if (sign == -1) + if (!int_part) { + if (neg) *p++ = '-'; *p++ = '0'; } else { - int ret; + int ret, i, n; while (int_part != 0) { - int_part2 = int_part / 10; - *p++ = (char)(int_part - ((int_part2 << 3) + (int_part2 << 1)) + '0'); - int_part = int_part2; + long long j = int_part / 10; + *p++ = (char)(int_part - ((j << 3) + (j << 1)) + '0'); + int_part = j; } - if (sign == -1) + if (neg) *p++ = '-'; /* Reverse string */ - ret = p - outbuf; + ret = p - buffer; for (i = 0, n = ret/2; i < n; i++) { - int j = ret - i - 1; - c = outbuf[i]; - outbuf[i] = outbuf[j]; - outbuf[j] = c; + int j = ret - i - 1; + char c = buffer[i]; + buffer[i] = buffer[j]; + buffer[j] = c; } } - if (decimals != 0) + + if (decimals > 0) { + int i; *p++ = '.'; - max = maxlen - (p - outbuf) - 1 /* leave room for trailing '\0' */; - if (max > decimals) + max = buffer_size - (p - buffer) - 1 /* leave room for trailing '\0' */; + + if (decimals > max) + return -1; /* the number is not large enough to fit in the buffer */ + max = decimals; - for (m = 0; m < max; m++) { - /* frac_part *= 10; */ - frac_part = (frac_part << 3) + (frac_part << 1); - *p++ = (char)((frac_part >> (FRAC_SIZE + 1)) + '0'); - frac_part &= FRAC_MASK2; - } + for (i = 0; i < max; i++) { + /* frac_part *= 10; */ + frac_part = (frac_part << 3) + (frac_part << 1); - roundup = 0; - /* Rounding - look at the next digit */ - frac_part = (frac_part << 3) + (frac_part << 1); - digit = (frac_part >> (FRAC_SIZE + 1)); - if (digit > 5) - roundup = 1; - else if (digit == 5) { - frac_part &= FRAC_MASK2; - if (frac_part != 0) roundup = 1; - } - if (roundup) { - char d; - int pos = p - outbuf - 1; - do { - d = outbuf[pos]; - if (d == '-') break; - if (d == '.') continue; - if (++d != ':') { - outbuf[pos] = d; - break; - } - outbuf[pos] = '0'; - } while (--pos); + *p++ = (char)((frac_part >> (FRAC_SIZE + 1)) + '0'); + frac_part &= FRAC_MASK2; + } + + /* Delete trailing zeroes */ + if (compact) + p = find_first_trailing_zero(p); } - /* Delete trailing zeroes */ - if (compact && *(p - 1) == '0') - p = float_first_trailing_zero(--p); *p = '\0'; - return p - outbuf; + return p - buffer; } -- cgit v1.2.3 From fc8ed627b5dc77cc294fcd207378cf803ba3f3dd Mon Sep 17 00:00:00 2001 From: Lukas Larsson Date: Fri, 8 Feb 2013 10:24:18 +0100 Subject: Use macros instead of constants This is needed as C90 (and therefore the win32 compiler) does not allow constants to be calculations based on other constants. --- erts/emulator/sys/common/erl_sys_common_misc.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) (limited to 'erts/emulator/sys/common/erl_sys_common_misc.c') diff --git a/erts/emulator/sys/common/erl_sys_common_misc.c b/erts/emulator/sys/common/erl_sys_common_misc.c index 5523b6fc0b..6cdf7ca0ed 100644 --- a/erts/emulator/sys/common/erl_sys_common_misc.c +++ b/erts/emulator/sys/common/erl_sys_common_misc.c @@ -125,11 +125,20 @@ sys_double_to_chars(double fp, char *buffer, size_t buffer_size) * if compact != 0, the trailing 0's will be truncated */ int -sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals, int compact) +sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals, + int compact) { - /* Note that some C compilers don't support "static const double" propagation into - * arrays so we use a define */ + /* Note that some C compilers don't support "static const" propagation + * so we use a defines */ #define SYS_DOUBLE_RND_CONST 0.55555555555555555 + #define FRAC_SIZE 52 + #define EXP_SIZE 11 + #define EXP_MASK ((1ll << EXP_SIZE) - 1) + #define MAX_DECIMALS (sizeof(cs_sys_double_pow10) \ + / sizeof(cs_sys_double_pow10[0])) + #define FRAC_MASK ((1ll << FRAC_SIZE) - 1) + #define FRAC_MASK2 ((1ll << (FRAC_SIZE + 1)) - 1) + #define MAX_FLOAT (1ll << (FRAC_SIZE+1)) static const double cs_sys_double_pow10[] = { SYS_DOUBLE_RND_CONST / 1ll, @@ -153,15 +162,6 @@ sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals, SYS_DOUBLE_RND_CONST / 1000000000000000000ll }; - static const int FRAC_SIZE = 52; - static const int EXP_SIZE = 11; - static const int EXP_MASK = (1ll << EXP_SIZE) - 1; - static const int MAX_DECIMALS = sizeof(cs_sys_double_pow10) / sizeof(cs_sys_double_pow10[0]); - - static const long long FRAC_MASK = (1ll << FRAC_SIZE) - 1; - static const long long FRAC_MASK2 = (1ll << (FRAC_SIZE + 1)) - 1; - static const long long MAX_FLOAT = 1ll << (FRAC_SIZE+1); - long long mantissa, int_part = 0, frac_part = 0; short exp; int max; -- cgit v1.2.3