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234 lines
7.4 KiB
C
234 lines
7.4 KiB
C
/*
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An alternative implementation of "strtod()" that is both
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simplier, and thread-safe.
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Original code from mit-threads as bundled with MySQL 3.23
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SQL:2003 specifies a number as
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<signed numeric literal> ::= [ <sign> ] <unsigned numeric literal>
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<unsigned numeric literal> ::=
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<exact numeric literal>
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| <approximate numeric literal>
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<exact numeric literal> ::=
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<unsigned integer> [ <period> [ <unsigned integer> ] ]
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| <period> <unsigned integer>
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<approximate numeric literal> ::= <mantissa> E <exponent>
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<mantissa> ::= <exact numeric literal>
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<exponent> ::= <signed integer>
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So do we.
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*/
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#include "my_base.h" /* Includes errno.h + EOVERFLOW */
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#include "m_ctype.h"
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#define MAX_DBL_EXP 308
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#define MAX_RESULT_FOR_MAX_EXP 1.7976931348623157
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const double log_10[] = {
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1e000, 1e001, 1e002, 1e003, 1e004, 1e005, 1e006, 1e007, 1e008, 1e009,
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1e010, 1e011, 1e012, 1e013, 1e014, 1e015, 1e016, 1e017, 1e018, 1e019,
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1e020, 1e021, 1e022, 1e023, 1e024, 1e025, 1e026, 1e027, 1e028, 1e029,
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1e030, 1e031, 1e032, 1e033, 1e034, 1e035, 1e036, 1e037, 1e038, 1e039,
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1e040, 1e041, 1e042, 1e043, 1e044, 1e045, 1e046, 1e047, 1e048, 1e049,
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1e050, 1e051, 1e052, 1e053, 1e054, 1e055, 1e056, 1e057, 1e058, 1e059,
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1e060, 1e061, 1e062, 1e063, 1e064, 1e065, 1e066, 1e067, 1e068, 1e069,
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1e070, 1e071, 1e072, 1e073, 1e074, 1e075, 1e076, 1e077, 1e078, 1e079,
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1e080, 1e081, 1e082, 1e083, 1e084, 1e085, 1e086, 1e087, 1e088, 1e089,
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1e090, 1e091, 1e092, 1e093, 1e094, 1e095, 1e096, 1e097, 1e098, 1e099,
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1e100, 1e101, 1e102, 1e103, 1e104, 1e105, 1e106, 1e107, 1e108, 1e109,
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1e110, 1e111, 1e112, 1e113, 1e114, 1e115, 1e116, 1e117, 1e118, 1e119,
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1e120, 1e121, 1e122, 1e123, 1e124, 1e125, 1e126, 1e127, 1e128, 1e129,
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1e130, 1e131, 1e132, 1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139,
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1e140, 1e141, 1e142, 1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149,
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1e150, 1e151, 1e152, 1e153, 1e154, 1e155, 1e156, 1e157, 1e158, 1e159,
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1e160, 1e161, 1e162, 1e163, 1e164, 1e165, 1e166, 1e167, 1e168, 1e169,
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1e170, 1e171, 1e172, 1e173, 1e174, 1e175, 1e176, 1e177, 1e178, 1e179,
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1e180, 1e181, 1e182, 1e183, 1e184, 1e185, 1e186, 1e187, 1e188, 1e189,
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1e190, 1e191, 1e192, 1e193, 1e194, 1e195, 1e196, 1e197, 1e198, 1e199,
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1e200, 1e201, 1e202, 1e203, 1e204, 1e205, 1e206, 1e207, 1e208, 1e209,
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1e210, 1e211, 1e212, 1e213, 1e214, 1e215, 1e216, 1e217, 1e218, 1e219,
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1e220, 1e221, 1e222, 1e223, 1e224, 1e225, 1e226, 1e227, 1e228, 1e229,
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1e230, 1e231, 1e232, 1e233, 1e234, 1e235, 1e236, 1e237, 1e238, 1e239,
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1e240, 1e241, 1e242, 1e243, 1e244, 1e245, 1e246, 1e247, 1e248, 1e249,
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1e250, 1e251, 1e252, 1e253, 1e254, 1e255, 1e256, 1e257, 1e258, 1e259,
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1e260, 1e261, 1e262, 1e263, 1e264, 1e265, 1e266, 1e267, 1e268, 1e269,
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1e270, 1e271, 1e272, 1e273, 1e274, 1e275, 1e276, 1e277, 1e278, 1e279,
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1e280, 1e281, 1e282, 1e283, 1e284, 1e285, 1e286, 1e287, 1e288, 1e289,
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1e290, 1e291, 1e292, 1e293, 1e294, 1e295, 1e296, 1e297, 1e298, 1e299,
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1e300, 1e301, 1e302, 1e303, 1e304, 1e305, 1e306, 1e307, 1e308
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};
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/*
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Convert string to double (string doesn't have to be null terminated)
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SYNOPSIS
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my_strtod()
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str String to convert
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end_ptr Pointer to pointer that points to end of string
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Will be updated to point to end of double.
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error Will contain error number in case of error (else 0)
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RETURN
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value of str as double
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*/
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double my_strtod(const char *str, char **end_ptr, int *error)
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{
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double result= 0.0;
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uint negative= 0, neg_exp= 0;
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size_t ndigits, dec_digits= 0;
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int exponent= 0, digits_after_dec_point= 0, tmp_exp, step;
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const char *old_str, *end= *end_ptr, *start_of_number;
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char next_char;
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my_bool overflow=0;
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double scaler= 1.0;
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*error= 0;
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if (str >= end)
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goto done;
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while (my_isspace(&my_charset_latin1, *str))
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{
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if (++str == end)
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goto done;
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}
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start_of_number= str;
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if ((negative= (*str == '-')) || *str=='+')
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{
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if (++str == end)
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goto done; /* Could be changed to error */
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}
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/* Skip pre-zero for easier calculation of overflows */
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while (*str == '0')
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{
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if (++str == end)
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goto done;
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start_of_number= 0; /* Found digit */
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}
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old_str= str;
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while ((next_char= *str) >= '0' && next_char <= '9')
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{
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result= result*10.0 + (next_char - '0');
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scaler= scaler*10.0;
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if (++str == end)
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{
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next_char= 0; /* Found end of string */
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break;
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}
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start_of_number= 0; /* Found digit */
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}
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ndigits= (size_t) (str-old_str);
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if (next_char == '.' && str < end-1)
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{
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/*
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Continue to add numbers after decimal point to the result, as if there
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was no decimal point. We will later (in the exponent handling) shift
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the number down with the required number of fractions. We do it this
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way to be able to get maximum precision for numbers like 123.45E+02,
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which are normal for some ODBC applications.
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*/
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old_str= ++str;
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while (my_isdigit(&my_charset_latin1, (next_char= *str)))
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{
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result= result*10.0 + (next_char - '0');
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digits_after_dec_point++;
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scaler= scaler*10.0;
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if (++str == end)
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{
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next_char= 0;
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break;
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}
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}
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/* If we found just '+.' or '.' then point at first character */
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if (!(dec_digits= (size_t) (str-old_str)) && start_of_number)
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str= start_of_number; /* Point at '+' or '.' */
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}
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if ((next_char == 'e' || next_char == 'E') &&
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dec_digits + ndigits != 0 && str < end-1)
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{
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const char *old_str2= str++;
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if ((neg_exp= (*str == '-')) || *str == '+')
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str++;
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if (str == end || !my_isdigit(&my_charset_latin1, *str))
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str= old_str2;
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else
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{
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do
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{
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if (exponent < 9999) /* prot. against exp overfl. */
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exponent= exponent*10 + (*str - '0');
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str++;
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} while (str < end && my_isdigit(&my_charset_latin1, *str));
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}
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}
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tmp_exp= (neg_exp ? exponent + digits_after_dec_point :
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exponent - digits_after_dec_point);
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if (tmp_exp)
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{
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int order;
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/*
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Check for underflow/overflow.
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order is such an integer number that f = C * 10 ^ order,
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where f is the resulting floating point number and 1 <= C < 10.
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Here we compute the modulus
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*/
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order= exponent + (neg_exp ? -1 : 1) * (ndigits - 1);
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if (order < 0)
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order= -order;
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if (order >= MAX_DBL_EXP && !neg_exp && result)
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{
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double c;
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/* Compute modulus of C (see comment above) */
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c= result / scaler * 10.0;
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if (order > MAX_DBL_EXP || c > MAX_RESULT_FOR_MAX_EXP)
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{
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overflow= 1;
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goto done;
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}
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}
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exponent= tmp_exp;
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if (exponent < 0)
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{
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exponent= -exponent;
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neg_exp= 1; /* neg_exp was 0 before */
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}
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step= array_elements(log_10) - 1;
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for (; exponent > step; exponent-= step)
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result= neg_exp ? result / log_10[step] : result * log_10[step];
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result= neg_exp ? result / log_10[exponent] : result * log_10[exponent];
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}
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done:
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*end_ptr= (char*) str; /* end of number */
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if (overflow || my_isinf(result))
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{
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result= DBL_MAX;
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*error= EOVERFLOW;
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}
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return negative ? -result : result;
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}
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double my_atof(const char *nptr)
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{
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int error;
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const char *end= nptr+65535; /* Should be enough */
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return (my_strtod(nptr, (char**) &end, &error));
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}
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