py/formatfloat.c - lite/micropython - Linaro Git Browser

 /*
  * This file is part of the Micro Python project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
  * Copyright (c) 2013, 2014 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 /***********************************************************************

   formatfloat.c  - Ruutine for converting a single-precision floating
                     point number into a string.

   The code in this funcion was inspired from Fred Bayer's pdouble.c.
   Since pdouble.c was released as Public Domain, I'm releasing this
   code as public domain as well.

   The original code can be found in https://github.com/dhylands/format-float

   Dave Hylands

 ***********************************************************************/

 #include <stdlib.h>
 #include <stdint.h>

 #include "py/mpconfig.h"

 #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT

 #include "py/formatfloat.h"

 // 1 sign bit, 8 exponent bits, and 23 mantissa bits.
 // exponent values 0 and 255 are reserved, exponent can be 1 to 254.
 // exponent is stored with a bias of 127.
 // The min and max floats are on the order of 1x10^37 and 1x10^-37

 #define FLT_SIGN_MASK   0x80000000
 #define FLT_EXP_MASK    0x7F800000
 #define FLT_MAN_MASK    0x007FFFFF

 static const float g_pos_pow[] = {
     1e32, 1e16, 1e8, 1e4, 1e2, 1e1
 };
 static const float g_neg_pow[] = {
     1e-32, 1e-16, 1e-8, 1e-4, 1e-2, 1e-1
 };

 int mp_format_float(float f, char *buf, size_t buf_size, char fmt, int prec, char sign) {

     char *s = buf;
     int buf_remaining = buf_size - 1;

     union {
         float f;
         uint32_t u;
     } num = {f};

     if (buf_size < 7) {
         // Smallest exp notion is -9e+99 which is 6 chars plus terminating
         // null.

         if (buf_size >= 2) {
             *s++ = '?';
         }
         if (buf_size >= 1) {
             *s++ = '\0';
         }
         return buf_size >= 2;
     }
     if (num.u & FLT_SIGN_MASK) {
         *s++ = '-';
         num.u &= ~FLT_SIGN_MASK;
     } else {
         if (sign) {
             *s++ = sign;
         }
     }
     buf_remaining -= (s - buf); // Adjust for sign

     if ((num.u & FLT_EXP_MASK) == FLT_EXP_MASK) {
         char uc = fmt & 0x20;
         if ((num.u & FLT_MAN_MASK) == 0) {
             *s++ = 'I' ^ uc;
             *s++ = 'N' ^ uc;
             *s++ = 'F' ^ uc;
         } else {
             *s++ = 'N' ^ uc;
             *s++ = 'A' ^ uc;
             *s++ = 'N' ^ uc;
         }
         *s = '\0';
         return s - buf;
     }

     if (prec < 0) {
         prec = 6;
     }
     char e_char = 'E' | (fmt & 0x20);   // e_char will match case of fmt
     fmt |= 0x20; // Force fmt to be lowercase
     char org_fmt = fmt;
     if (fmt == 'g' && prec == 0) {
         prec = 1;
     }
     int e, e1;
     int dec = 0;
     char e_sign = '\0';
     int num_digits = 0;
     const float *pos_pow = g_pos_pow;
     const float *neg_pow = g_neg_pow;

     if (num.u == 0) {
         e = 0;
         if (fmt == 'e') {
             e_sign = '+';
         } else if (fmt == 'f') {
             num_digits = prec + 1;
         }
     } else if (num.u < 0x3f800000) { // f < 1.0
         // Build negative exponent
         for (e = 0, e1 = 32; e1; e1 >>= 1, pos_pow++, neg_pow++) {
             if (*neg_pow > num.f) {
                 e += e1;
                 num.f *= *pos_pow;
             }
         }
         if (num.f < 1.0F && num.f >= 0.9999995F) {
             num.f = 1.0F;
         } else {
             e++;
             num.f *= 10.0F;
         }

         // If the user specified 'g' format, and e is <= 4, then we'll switch
         // to the fixed format ('f')

         if (fmt == 'f' || (fmt == 'g' && e <= 4)) {
             fmt = 'f';
             dec = -1;
             *s++ = '0';

             if (prec + e + 1 > buf_remaining) {
                 prec = buf_remaining - e - 1;
             }

             if (org_fmt == 'g') {
                 prec += (e - 1);
             }
             num_digits = prec;
             if (num_digits) {
                 *s++ = '.';
                 while (--e && num_digits) {
                     *s++ = '0';
                     num_digits--;
                 }
             }
         } else {
             // For e & g formats, we'll be printing the exponent, so set the
             // sign.
             e_sign = '-';
             dec = 0;

             if (prec > (buf_remaining - 6)) {
                 prec = buf_remaining - 6;
                 if (fmt == 'g') {
                     prec++;
                 }
             }
         }
     } else {
         // Build positive exponent
         for (e = 0, e1 = 32; e1; e1 >>= 1, pos_pow++, neg_pow++) {
             if (*pos_pow <= num.f) {
                 e += e1;
                 num.f *= *neg_pow;
             }
         }

         // If the user specified fixed format (fmt == 'f') and e makes the
         // number too big to fit into the available buffer, then we'll
         // switch to the 'e' format.

         if (fmt == 'f') {
             if (e >= buf_remaining) {
                 fmt = 'e';
             } else if ((e + prec + 2) > buf_remaining) {
                 prec = buf_remaining - e - 2;
                 if (prec < 0) {
                     // This means no decimal point, so we can add one back
                     // for the decimal.
                     prec++;
                 }
             }
         }
         if (fmt == 'e' && prec > (buf_remaining - 6)) {
             prec = buf_remaining - 6;
         }
         // If the user specified 'g' format, and e is < prec, then we'll switch
         // to the fixed format.

         if (fmt == 'g' && e < prec) {
             fmt = 'f';
             prec -= (e + 1);
         }
         if (fmt == 'f') {
             dec = e;
             num_digits = prec + e + 1;
         } else {
             e_sign = '+';
         }
     }
     if (prec < 0) {
         // This can happen when the prec is trimmed to prevent buffer overflow
         prec = 0;
     }

     // We now have num.f as a floating point number between >= 1 and < 10
     // (or equal to zero), and e contains the absolute value of the power of
     // 10 exponent. and (dec + 1) == the number of dgits before the decimal.

     // For e, prec is # digits after the decimal
     // For f, prec is # digits after the decimal
     // For g, prec is the max number of significant digits
     //
     // For e & g there will be a single digit before the decimal
     // for f there will be e digits before the decimal

     if (fmt == 'e') {
         num_digits = prec + 1;
     } else if (fmt == 'g') {
         if (prec == 0) {
             prec = 1;
         }
         num_digits = prec;
     }

     // Print the digits of the mantissa
     for (int i = 0; i < num_digits; ++i, --dec) {
         int32_t d = num.f;
         *s++ = '0' + d;
         if (dec == 0 && prec > 0) {
             *s++ = '.';
         }
         num.f -= (float)d;
         num.f *= 10.0F;
     }

     // Round
     if (num.f >= 5.0F) {
         char *rs = s;
         rs--;
         while (1) {
             if (*rs == '.') {
                 rs--;
                 continue;
             }
             if (*rs < '0' || *rs > '9') {
                 // + or -
                 rs++; // So we sit on the digit to the right of the sign
                 break;
             }
             if (*rs < '9') {
                 (*rs)++;
                 break;
             }
             *rs = '0';
             if (rs == buf) {
                 break;
             }
             rs--;
         }
         if (*rs == '0') {
             // We need to insert a 1
             if (rs[1] == '.' && fmt != 'f') {
                 // We're going to round 9.99 to 10.00
                 // Move the decimal point
                 rs[0] = '.';
                 rs[1] = '0';
                 if (e_sign == '-') {
                     e--;
                 } else {
                     e++;
                 }
             }
             s++;
             char *ss = s;
             while (ss > rs) {
                 *ss = ss[-1];
                 ss--;
             }
             *rs = '1';
         }
         if (num.u < 0x3f800000 && fmt == 'f') {
             // We rounded up to 1.0
             prec--;
         }
     }

     if (org_fmt == 'g' && prec > 0) {
         // Remove trailing zeros and a trailing decimal point
         while (s[-1] == '0') {
             s--;
         }
         if (s[-1] == '.') {
             s--;
         }
     }
     // Append the exponent
     if (e_sign) {
         *s++ = e_char;
         *s++ = e_sign;
         *s++ = '0' + (e / 10);
         *s++ = '0' + (e % 10);
     }
     *s = '\0';

     return s - buf;
 }

 #endif
	/*
	* This file is part of the Micro Python project, http://micropython.org/
	*
	* The MIT License (MIT)
	*
	* Copyright (c) 2013, 2014 Damien P. George
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	/***********************************************************************

	formatfloat.c - Ruutine for converting a single-precision floating
	point number into a string.

	The code in this funcion was inspired from Fred Bayer's pdouble.c.
	Since pdouble.c was released as Public Domain, I'm releasing this
	code as public domain as well.

	The original code can be found in https://github.com/dhylands/format-float

	Dave Hylands

	***********************************************************************/

	#include <stdlib.h>
	#include <stdint.h>

	#include "py/mpconfig.h"

	#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT

	#include "py/formatfloat.h"

	// 1 sign bit, 8 exponent bits, and 23 mantissa bits.
	// exponent values 0 and 255 are reserved, exponent can be 1 to 254.
	// exponent is stored with a bias of 127.
	// The min and max floats are on the order of 1x10^37 and 1x10^-37

	#define FLT_SIGN_MASK 0x80000000
	#define FLT_EXP_MASK 0x7F800000
	#define FLT_MAN_MASK 0x007FFFFF

	static const float g_pos_pow[] = {
	1e32, 1e16, 1e8, 1e4, 1e2, 1e1
	};
	static const float g_neg_pow[] = {
	1e-32, 1e-16, 1e-8, 1e-4, 1e-2, 1e-1
	};

	int mp_format_float(float f, char *buf, size_t buf_size, char fmt, int prec, char sign) {

	char *s = buf;
	int buf_remaining = buf_size - 1;

	union {
	float f;
	uint32_t u;
	} num = {f};

	if (buf_size < 7) {
	// Smallest exp notion is -9e+99 which is 6 chars plus terminating
	// null.

	if (buf_size >= 2) {
	*s++ = '?';
	}
	if (buf_size >= 1) {
	*s++ = '\0';
	}
	return buf_size >= 2;
	}
	if (num.u & FLT_SIGN_MASK) {
	*s++ = '-';
	num.u &= ~FLT_SIGN_MASK;
	} else {
	if (sign) {
	*s++ = sign;
	}
	}
	buf_remaining -= (s - buf); // Adjust for sign

	if ((num.u & FLT_EXP_MASK) == FLT_EXP_MASK) {
	char uc = fmt & 0x20;
	if ((num.u & FLT_MAN_MASK) == 0) {
	*s++ = 'I' ^ uc;
	*s++ = 'N' ^ uc;
	*s++ = 'F' ^ uc;
	} else {
	*s++ = 'N' ^ uc;
	*s++ = 'A' ^ uc;
	*s++ = 'N' ^ uc;
	}
	*s = '\0';
	return s - buf;
	}

	if (prec < 0) {
	prec = 6;
	}
	char e_char = 'E' \| (fmt & 0x20); // e_char will match case of fmt
	fmt \|= 0x20; // Force fmt to be lowercase
	char org_fmt = fmt;
	if (fmt == 'g' && prec == 0) {
	prec = 1;
	}
	int e, e1;
	int dec = 0;
	char e_sign = '\0';
	int num_digits = 0;
	const float *pos_pow = g_pos_pow;
	const float *neg_pow = g_neg_pow;

	if (num.u == 0) {
	e = 0;
	if (fmt == 'e') {
	e_sign = '+';
	} else if (fmt == 'f') {
	num_digits = prec + 1;
	}
	} else if (num.u < 0x3f800000) { // f < 1.0
	// Build negative exponent
	for (e = 0, e1 = 32; e1; e1 >>= 1, pos_pow++, neg_pow++) {
	if (*neg_pow > num.f) {
	e += e1;
	num.f = pos_pow;
	}
	}
	if (num.f < 1.0F && num.f >= 0.9999995F) {
	num.f = 1.0F;
	} else {
	e++;
	num.f *= 10.0F;
	}

	// If the user specified 'g' format, and e is <= 4, then we'll switch
	// to the fixed format ('f')

	if (fmt == 'f' \|\| (fmt == 'g' && e <= 4)) {
	fmt = 'f';
	dec = -1;
	*s++ = '0';

	if (prec + e + 1 > buf_remaining) {
	prec = buf_remaining - e - 1;
	}

	if (org_fmt == 'g') {
	prec += (e - 1);
	}
	num_digits = prec;
	if (num_digits) {
	*s++ = '.';
	while (--e && num_digits) {
	*s++ = '0';
	num_digits--;
	}
	}
	} else {
	// For e & g formats, we'll be printing the exponent, so set the
	// sign.
	e_sign = '-';
	dec = 0;

	if (prec > (buf_remaining - 6)) {
	prec = buf_remaining - 6;
	if (fmt == 'g') {
	prec++;
	}
	}
	}
	} else {
	// Build positive exponent
	for (e = 0, e1 = 32; e1; e1 >>= 1, pos_pow++, neg_pow++) {
	if (*pos_pow <= num.f) {
	e += e1;
	num.f = neg_pow;
	}
	}

	// If the user specified fixed format (fmt == 'f') and e makes the
	// number too big to fit into the available buffer, then we'll
	// switch to the 'e' format.

	if (fmt == 'f') {
	if (e >= buf_remaining) {
	fmt = 'e';
	} else if ((e + prec + 2) > buf_remaining) {
	prec = buf_remaining - e - 2;
	if (prec < 0) {
	// This means no decimal point, so we can add one back
	// for the decimal.
	prec++;
	}
	}
	}
	if (fmt == 'e' && prec > (buf_remaining - 6)) {
	prec = buf_remaining - 6;
	}
	// If the user specified 'g' format, and e is < prec, then we'll switch
	// to the fixed format.

	if (fmt == 'g' && e < prec) {
	fmt = 'f';
	prec -= (e + 1);
	}
	if (fmt == 'f') {
	dec = e;
	num_digits = prec + e + 1;
	} else {
	e_sign = '+';
	}
	}
	if (prec < 0) {
	// This can happen when the prec is trimmed to prevent buffer overflow
	prec = 0;
	}

	// We now have num.f as a floating point number between >= 1 and < 10
	// (or equal to zero), and e contains the absolute value of the power of
	// 10 exponent. and (dec + 1) == the number of dgits before the decimal.

	// For e, prec is # digits after the decimal
	// For f, prec is # digits after the decimal
	// For g, prec is the max number of significant digits
	//
	// For e & g there will be a single digit before the decimal
	// for f there will be e digits before the decimal

	if (fmt == 'e') {
	num_digits = prec + 1;
	} else if (fmt == 'g') {
	if (prec == 0) {
	prec = 1;
	}
	num_digits = prec;
	}

	// Print the digits of the mantissa
	for (int i = 0; i < num_digits; ++i, --dec) {
	int32_t d = num.f;
	*s++ = '0' + d;
	if (dec == 0 && prec > 0) {
	*s++ = '.';
	}
	num.f -= (float)d;
	num.f *= 10.0F;
	}

	// Round
	if (num.f >= 5.0F) {
	char *rs = s;
	rs--;
	while (1) {
	if (*rs == '.') {
	rs--;
	continue;
	}
	if (rs < '0' \|\| rs > '9') {
	// + or -
	rs++; // So we sit on the digit to the right of the sign
	break;
	}
	if (*rs < '9') {
	(*rs)++;
	break;
	}
	*rs = '0';
	if (rs == buf) {
	break;
	}
	rs--;
	}
	if (*rs == '0') {
	// We need to insert a 1
	if (rs[1] == '.' && fmt != 'f') {
	// We're going to round 9.99 to 10.00
	// Move the decimal point
	rs[0] = '.';
	rs[1] = '0';
	if (e_sign == '-') {
	e--;
	} else {
	e++;
	}
	}
	s++;
	char *ss = s;
	while (ss > rs) {
	*ss = ss[-1];
	ss--;
	}
	*rs = '1';
	}
	if (num.u < 0x3f800000 && fmt == 'f') {
	// We rounded up to 1.0
	prec--;
	}
	}

	if (org_fmt == 'g' && prec > 0) {
	// Remove trailing zeros and a trailing decimal point
	while (s[-1] == '0') {
	s--;
	}
	if (s[-1] == '.') {
	s--;
	}
	}
	// Append the exponent
	if (e_sign) {
	*s++ = e_char;
	*s++ = e_sign;
	*s++ = '0' + (e / 10);
	*s++ = '0' + (e % 10);
	}
	*s = '\0';

	return s - buf;
	}

	#endif