From 6ddfc4b3206f7177d0a0feac64350fbd2b99669c Mon Sep 17 00:00:00 2001
From: JiXieShi <lydxh935227514@gmail.com>
Date: Thu, 20 Jun 2024 21:46:32 +0800
Subject: [PATCH] UP

---
 lib/inc/printf/printf.h | 118 +++++
 lib/src/printf/printf.c | 935 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 1053 insertions(+)
 create mode 100644 lib/inc/printf/printf.h
 create mode 100644 lib/src/printf/printf.c

diff --git a/lib/inc/printf/printf.h b/lib/inc/printf/printf.h
new file mode 100644
index 0000000..638c83d
--- /dev/null
+++ b/lib/inc/printf/printf.h
@@ -0,0 +1,118 @@
+///////////////////////////////////////////////////////////////////////////////
+// \author (c) Marco Paland (info@paland.com)
+//             2014-2019, PALANDesign Hannover, Germany
+//
+// \license The MIT License (MIT)
+//
+// 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.
+//
+// \brief Tiny printf, sprintf and snprintf implementation, optimized for speed on
+//        embedded systems with a very limited resources.
+//        Use this instead of bloated standard/newlib printf.
+//        These routines are thread safe and reentrant.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _PRINTF_H_
+#define _PRINTF_H_
+
+#include <stdarg.h>
+#include <stddef.h>
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/**
+ * Output a character to a custom device like UART, used by the printf() function
+ * This function is declared here only. You have to write your custom implementation somewhere
+ * \param character Character to output
+ */
+void _putchar(char character);
+
+
+/**
+ * Tiny printf implementation
+ * You have to implement _putchar if you use printf()
+ * To avoid conflicts with the regular printf() API it is overridden by macro defines
+ * and internal underscore-appended functions like printf_() are used
+ * \param format A string that specifies the format of the output
+ * \return The number of characters that are written into the array, not counting the terminating null character
+ */
+//#define printf printf_
+int printf_(const char *format, ...);
+
+
+/**
+ * Tiny sprintf implementation
+ * Due to security reasons (buffer overflow) YOU SHOULD CONSIDER USING (V)SNPRINTF INSTEAD!
+ * \param buffer A pointer to the buffer where to store the formatted string. MUST be big enough to store the output!
+ * \param format A string that specifies the format of the output
+ * \return The number of characters that are WRITTEN into the buffer, not counting the terminating null character
+ */
+//#define sprintf sprintf_
+int sprintf_(char *buffer, const char *format, ...);
+
+
+/**
+ * Tiny snprintf/vsnprintf implementation
+ * \param buffer A pointer to the buffer where to store the formatted string
+ * \param count The maximum number of characters to store in the buffer, including a terminating null character
+ * \param format A string that specifies the format of the output
+ * \param va A value identifying a variable arguments list
+ * \return The number of characters that COULD have been written into the buffer, not counting the terminating
+ *         null character. A value equal or larger than count indicates truncation. Only when the returned value
+ *         is non-negative and less than count, the string has been completely written.
+ */
+//#define snprintf  snprintf_
+//#define vsnprintf vsnprintf_
+int snprintf_(char *buffer, size_t count, const char *format, ...);
+
+int vsnprintf_(char *buffer, size_t count, const char *format, va_list va);
+
+
+/**
+ * Tiny vprintf implementation
+ * \param format A string that specifies the format of the output
+ * \param va A value identifying a variable arguments list
+ * \return The number of characters that are WRITTEN into the buffer, not counting the terminating null character
+ */
+//#define vprintf vprintf_
+int vprintf_(const char *format, va_list va);
+
+
+/**
+ * printf with output function
+ * You may use this as dynamic alternative to printf() with its fixed _putchar() output
+ * \param out An output function which takes one character and an argument pointer
+ * \param arg An argument pointer for user data passed to output function
+ * \param format A string that specifies the format of the output
+ * \return The number of characters that are sent to the output function, not counting the terminating null character
+ */
+int fctprintf(void (*out)(char character, void *arg), void *arg, const char *format, ...);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif  // _PRINTF_H_
diff --git a/lib/src/printf/printf.c b/lib/src/printf/printf.c
new file mode 100644
index 0000000..8116ff7
--- /dev/null
+++ b/lib/src/printf/printf.c
@@ -0,0 +1,935 @@
+///////////////////////////////////////////////////////////////////////////////
+// \author (c) Marco Paland (info@paland.com)
+//             2014-2019, PALANDesign Hannover, Germany
+//
+// \license The MIT License (MIT)
+//
+// 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.
+//
+// \brief Tiny printf, sprintf and (v)snprintf implementation, optimized for speed on
+//        embedded systems with a very limited resources. These routines are thread
+//        safe and reentrant!
+//        Use this instead of the bloated standard/newlib printf cause these use
+//        malloc for printf (and may not be thread safe).
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "printf.h"
+
+
+// define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
+// printf_config.h header file
+// default: undefined
+#ifdef PRINTF_INCLUDE_CONFIG_H
+#include "printf_config.h"
+#endif
+
+
+// 'ntoa' conversion buffer size, this must be big enough to hold one converted
+// numeric number including padded zeros (dynamically created on stack)
+// default: 32 byte
+#ifndef PRINTF_NTOA_BUFFER_SIZE
+#define PRINTF_NTOA_BUFFER_SIZE    32U
+#endif
+
+// 'ftoa' conversion buffer size, this must be big enough to hold one converted
+// float number including padded zeros (dynamically created on stack)
+// default: 32 byte
+#ifndef PRINTF_FTOA_BUFFER_SIZE
+#define PRINTF_FTOA_BUFFER_SIZE    32U
+#endif
+
+// support for the floating point type (%f)
+// default: activated
+#ifndef PRINTF_DISABLE_SUPPORT_FLOAT
+#define PRINTF_SUPPORT_FLOAT
+#endif
+
+// support for exponential floating point notation (%e/%g)
+// default: activated
+#ifndef PRINTF_DISABLE_SUPPORT_EXPONENTIAL
+#define PRINTF_SUPPORT_EXPONENTIAL
+#endif
+
+// define the default floating point precision
+// default: 6 digits
+#ifndef PRINTF_DEFAULT_FLOAT_PRECISION
+#define PRINTF_DEFAULT_FLOAT_PRECISION  6U
+#endif
+
+// define the largest float suitable to print with %f
+// default: 1e9
+#ifndef PRINTF_MAX_FLOAT
+#define PRINTF_MAX_FLOAT  1e9
+#endif
+
+// support for the long long types (%llu or %p)
+// default: activated
+#ifndef PRINTF_DISABLE_SUPPORT_LONG_LONG
+#define PRINTF_SUPPORT_LONG_LONG
+#endif
+
+// support for the ptrdiff_t type (%t)
+// ptrdiff_t is normally defined in <stddef.h> as long or long long type
+// default: activated
+#ifndef PRINTF_DISABLE_SUPPORT_PTRDIFF_T
+#define PRINTF_SUPPORT_PTRDIFF_T
+#endif
+
+///////////////////////////////////////////////////////////////////////////////
+
+// internal flag definitions
+#define FLAGS_ZEROPAD   (1U <<  0U)
+#define FLAGS_LEFT      (1U <<  1U)
+#define FLAGS_PLUS      (1U <<  2U)
+#define FLAGS_SPACE     (1U <<  3U)
+#define FLAGS_HASH      (1U <<  4U)
+#define FLAGS_UPPERCASE (1U <<  5U)
+#define FLAGS_CHAR      (1U <<  6U)
+#define FLAGS_SHORT     (1U <<  7U)
+#define FLAGS_LONG      (1U <<  8U)
+#define FLAGS_LONG_LONG (1U <<  9U)
+#define FLAGS_PRECISION (1U << 10U)
+#define FLAGS_ADAPT_EXP (1U << 11U)
+
+
+// import float.h for DBL_MAX
+#if defined(PRINTF_SUPPORT_FLOAT)
+
+#include <float.h>
+
+#endif
+
+
+// output function type
+typedef void (*out_fct_type)(char character, void *buffer, size_t idx, size_t maxlen);
+
+
+// wrapper (used as buffer) for output function type
+typedef struct {
+    void (*fct)(char character, void *arg);
+
+    void *arg;
+} out_fct_wrap_type;
+
+
+// internal buffer output
+static inline void _out_buffer(char character, void *buffer, size_t idx, size_t maxlen) {
+    if (idx < maxlen) {
+        ((char *) buffer)[idx] = character;
+    }
+}
+
+
+// internal null output
+static inline void _out_null(char character, void *buffer, size_t idx, size_t maxlen) {
+    (void) character;
+    (void) buffer;
+    (void) idx;
+    (void) maxlen;
+}
+
+
+// internal _putchar wrapper
+static inline void _out_char(char character, void *buffer, size_t idx, size_t maxlen) {
+    (void) buffer;
+    (void) idx;
+    (void) maxlen;
+    if (character) {
+
+    }
+}
+
+
+// internal output function wrapper
+static inline void _out_fct(char character, void *buffer, size_t idx, size_t maxlen) {
+    (void) idx;
+    (void) maxlen;
+    if (character) {
+        // buffer is the output fct pointer
+        ((out_fct_wrap_type *) buffer)->fct(character, ((out_fct_wrap_type *) buffer)->arg);
+    }
+}
+
+
+// internal secure strlen
+// \return The length of the string (excluding the terminating 0) limited by 'maxsize'
+static inline unsigned int _strnlen_s(const char *str, size_t maxsize) {
+    const char *s;
+    for (s = str; *s && maxsize--; ++s);
+    return (unsigned int) (s - str);
+}
+
+
+// internal test if char is a digit (0-9)
+// \return true if char is a digit
+static inline bool _is_digit(char ch) {
+    return (ch >= '0') && (ch <= '9');
+}
+
+
+// internal ASCII string to unsigned int conversion
+static unsigned int _atoi(const char **str) {
+    unsigned int i = 0U;
+    while (_is_digit(**str)) {
+        i = i * 10U + (unsigned int) (*((*str)++) - '0');
+    }
+    return i;
+}
+
+
+// output the specified string in reverse, taking care of any zero-padding
+static size_t
+_out_rev(out_fct_type out, char *buffer, size_t idx, size_t maxlen, const char *buf, size_t len, unsigned int width,
+         unsigned int flags) {
+    const size_t start_idx = idx;
+
+    // pad spaces up to given width
+    if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
+        for (size_t i = len; i < width; i++) {
+            out(' ', buffer, idx++, maxlen);
+        }
+    }
+
+    // reverse string
+    while (len) {
+        out(buf[--len], buffer, idx++, maxlen);
+    }
+
+    // append pad spaces up to given width
+    if (flags & FLAGS_LEFT) {
+        while (idx - start_idx < width) {
+            out(' ', buffer, idx++, maxlen);
+        }
+    }
+
+    return idx;
+}
+
+
+// internal itoa format
+static size_t
+_ntoa_format(out_fct_type out, char *buffer, size_t idx, size_t maxlen, char *buf, size_t len, bool negative,
+             unsigned int base, unsigned int prec, unsigned int width, unsigned int flags) {
+    // pad leading zeros
+    if (!(flags & FLAGS_LEFT)) {
+        if (width && (flags & FLAGS_ZEROPAD) && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
+            width--;
+        }
+        while ((len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
+            buf[len++] = '0';
+        }
+        while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
+            buf[len++] = '0';
+        }
+    }
+
+    // handle hash
+    if (flags & FLAGS_HASH) {
+        if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) {
+            len--;
+            if (len && (base == 16U)) {
+                len--;
+            }
+        }
+        if ((base == 16U) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
+            buf[len++] = 'x';
+        } else if ((base == 16U) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
+            buf[len++] = 'X';
+        } else if ((base == 2U) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
+            buf[len++] = 'b';
+        }
+        if (len < PRINTF_NTOA_BUFFER_SIZE) {
+            buf[len++] = '0';
+        }
+    }
+
+    if (len < PRINTF_NTOA_BUFFER_SIZE) {
+        if (negative) {
+            buf[len++] = '-';
+        } else if (flags & FLAGS_PLUS) {
+            buf[len++] = '+';  // ignore the space if the '+' exists
+        } else if (flags & FLAGS_SPACE) {
+            buf[len++] = ' ';
+        }
+    }
+
+    return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
+}
+
+
+// internal itoa for 'long' type
+static size_t _ntoa_long(out_fct_type out, char *buffer, size_t idx, size_t maxlen, unsigned long value, bool negative,
+                         unsigned long base, unsigned int prec, unsigned int width, unsigned int flags) {
+    char buf[PRINTF_NTOA_BUFFER_SIZE];
+    size_t len = 0U;
+
+    // no hash for 0 values
+    if (!value) {
+        flags &= ~FLAGS_HASH;
+    }
+
+    // write if precision != 0 and value is != 0
+    if (!(flags & FLAGS_PRECISION) || value) {
+        do {
+            const char digit = (char) (value % base);
+            buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
+            value /= base;
+        } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
+    }
+
+    return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int) base, prec, width, flags);
+}
+
+
+// internal itoa for 'long long' type
+#if defined(PRINTF_SUPPORT_LONG_LONG)
+
+static size_t
+_ntoa_long_long(out_fct_type out, char *buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative,
+                unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags) {
+    char buf[PRINTF_NTOA_BUFFER_SIZE];
+    size_t len = 0U;
+
+    // no hash for 0 values
+    if (!value) {
+        flags &= ~FLAGS_HASH;
+    }
+
+    // write if precision != 0 and value is != 0
+    if (!(flags & FLAGS_PRECISION) || value) {
+        do {
+            const char digit = (char) (value % base);
+            buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
+            value /= base;
+        } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
+    }
+
+    return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int) base, prec, width, flags);
+}
+
+#endif  // PRINTF_SUPPORT_LONG_LONG
+
+
+#if defined(PRINTF_SUPPORT_FLOAT)
+
+#if defined(PRINTF_SUPPORT_EXPONENTIAL)
+
+// forward declaration so that _ftoa can switch to exp notation for values > PRINTF_MAX_FLOAT
+static size_t
+_etoa(out_fct_type out, char *buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width,
+      unsigned int flags);
+
+#endif
+
+
+// internal ftoa for fixed decimal floating point
+static size_t
+_ftoa(out_fct_type out, char *buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width,
+      unsigned int flags) {
+    char buf[PRINTF_FTOA_BUFFER_SIZE];
+    size_t len = 0U;
+    double diff = 0.0;
+
+    // powers of 10
+    static const double pow10[] = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000};
+
+    // test for special values
+    if (value != value)
+        return _out_rev(out, buffer, idx, maxlen, "nan", 3, width, flags);
+    if (value < -DBL_MAX)
+        return _out_rev(out, buffer, idx, maxlen, "fni-", 4, width, flags);
+    if (value > DBL_MAX)
+        return _out_rev(out, buffer, idx, maxlen, (flags & FLAGS_PLUS) ? "fni+" : "fni", (flags & FLAGS_PLUS) ? 4U : 3U,
+                        width, flags);
+
+    // test for very large values
+    // standard printf behavior is to print EVERY whole number digit -- which could be 100s of characters overflowing your buffers == bad
+    if ((value > PRINTF_MAX_FLOAT) || (value < -PRINTF_MAX_FLOAT)) {
+#if defined(PRINTF_SUPPORT_EXPONENTIAL)
+        return _etoa(out, buffer, idx, maxlen, value, prec, width, flags);
+#else
+        return 0U;
+#endif
+    }
+
+    // test for negative
+    bool negative = false;
+    if (value < 0) {
+        negative = true;
+        value = 0 - value;
+    }
+
+    // set default precision, if not set explicitly
+    if (!(flags & FLAGS_PRECISION)) {
+        prec = PRINTF_DEFAULT_FLOAT_PRECISION;
+    }
+    // limit precision to 9, cause a prec >= 10 can lead to overflow errors
+    while ((len < PRINTF_FTOA_BUFFER_SIZE) && (prec > 9U)) {
+        buf[len++] = '0';
+        prec--;
+    }
+
+    int whole = (int) value;
+    double tmp = (value - whole) * pow10[prec];
+    unsigned long frac = (unsigned long) tmp;
+    diff = tmp - frac;
+
+    if (diff > 0.5) {
+        ++frac;
+        // handle rollover, e.g. case 0.99 with prec 1 is 1.0
+        if (frac >= pow10[prec]) {
+            frac = 0;
+            ++whole;
+        }
+    } else if (diff < 0.5) {
+    } else if ((frac == 0U) || (frac & 1U)) {
+        // if halfway, round up if odd OR if last digit is 0
+        ++frac;
+    }
+
+    if (prec == 0U) {
+        diff = value - (double) whole;
+        if ((!(diff < 0.5) || (diff > 0.5)) && (whole & 1)) {
+            // exactly 0.5 and ODD, then round up
+            // 1.5 -> 2, but 2.5 -> 2
+            ++whole;
+        }
+    } else {
+        unsigned int count = prec;
+        // now do fractional part, as an unsigned number
+        while (len < PRINTF_FTOA_BUFFER_SIZE) {
+            --count;
+            buf[len++] = (char) (48U + (frac % 10U));
+            if (!(frac /= 10U)) {
+                break;
+            }
+        }
+        // add extra 0s
+        while ((len < PRINTF_FTOA_BUFFER_SIZE) && (count-- > 0U)) {
+            buf[len++] = '0';
+        }
+        if (len < PRINTF_FTOA_BUFFER_SIZE) {
+            // add decimal
+            buf[len++] = '.';
+        }
+    }
+
+    // do whole part, number is reversed
+    while (len < PRINTF_FTOA_BUFFER_SIZE) {
+        buf[len++] = (char) (48 + (whole % 10));
+        if (!(whole /= 10)) {
+            break;
+        }
+    }
+
+    // pad leading zeros
+    if (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD)) {
+        if (width && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
+            width--;
+        }
+        while ((len < width) && (len < PRINTF_FTOA_BUFFER_SIZE)) {
+            buf[len++] = '0';
+        }
+    }
+
+    if (len < PRINTF_FTOA_BUFFER_SIZE) {
+        if (negative) {
+            buf[len++] = '-';
+        } else if (flags & FLAGS_PLUS) {
+            buf[len++] = '+';  // ignore the space if the '+' exists
+        } else if (flags & FLAGS_SPACE) {
+            buf[len++] = ' ';
+        }
+    }
+
+    return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
+}
+
+
+#if defined(PRINTF_SUPPORT_EXPONENTIAL)
+
+// internal ftoa variant for exponential floating-point type, contributed by Martijn Jasperse <m.jasperse@gmail.com>
+static size_t
+_etoa(out_fct_type out, char *buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width,
+      unsigned int flags) {
+    // check for NaN and special values
+    if ((value != value) || (value > DBL_MAX) || (value < -DBL_MAX)) {
+        return _ftoa(out, buffer, idx, maxlen, value, prec, width, flags);
+    }
+
+    // determine the sign
+    const bool negative = value < 0;
+    if (negative) {
+        value = -value;
+    }
+
+    // default precision
+    if (!(flags & FLAGS_PRECISION)) {
+        prec = PRINTF_DEFAULT_FLOAT_PRECISION;
+    }
+
+    // determine the decimal exponent
+    // based on the algorithm by David Gay (https://www.ampl.com/netlib/fp/dtoa.c)
+    union {
+        uint64_t U;
+        double F;
+    } conv;
+
+    conv.F = value;
+    int exp2 = (int) ((conv.U >> 52U) & 0x07FFU) - 1023;           // effectively log2
+    conv.U = (conv.U & ((1ULL << 52U) - 1U)) | (1023ULL << 52U);  // drop the exponent so conv.F is now in [1,2)
+    // now approximate log10 from the log2 integer part and an expansion of ln around 1.5
+    int expval = (int) (0.1760912590558 + exp2 * 0.301029995663981 + (conv.F - 1.5) * 0.289529654602168);
+    // now we want to compute 10^expval but we want to be sure it won't overflow
+    exp2 = (int) (expval * 3.321928094887362 + 0.5);
+    const double z = expval * 2.302585092994046 - exp2 * 0.6931471805599453;
+    const double z2 = z * z;
+    conv.U = (uint64_t) (exp2 + 1023) << 52U;
+    // compute exp(z) using continued fractions, see https://en.wikipedia.org/wiki/Exponential_function#Continued_fractions_for_ex
+    conv.F *= 1 + 2 * z / (2 - z + (z2 / (6 + (z2 / (10 + z2 / 14)))));
+    // correct for rounding errors
+    if (value < conv.F) {
+        expval--;
+        conv.F /= 10;
+    }
+
+    // the exponent format is "%+03d" and largest value is "307", so set aside 4-5 characters
+    unsigned int minwidth = ((expval < 100) && (expval > -100)) ? 4U : 5U;
+
+    // in "%g" mode, "prec" is the number of *significant figures* not decimals
+    if (flags & FLAGS_ADAPT_EXP) {
+        // do we want to fall-back to "%f" mode?
+        if ((value >= 1e-4) && (value < 1e6)) {
+            if ((int) prec > expval) {
+                prec = (unsigned) ((int) prec - expval - 1);
+            } else {
+                prec = 0;
+            }
+            flags |= FLAGS_PRECISION;   // make sure _ftoa respects precision
+            // no characters in exponent
+            minwidth = 0U;
+            expval = 0;
+        } else {
+            // we use one sigfig for the whole part
+            if ((prec > 0) && (flags & FLAGS_PRECISION)) {
+                --prec;
+            }
+        }
+    }
+
+    // will everything fit?
+    unsigned int fwidth = width;
+    if (width > minwidth) {
+        // we didn't fall-back so subtract the characters required for the exponent
+        fwidth -= minwidth;
+    } else {
+        // not enough characters, so go back to default sizing
+        fwidth = 0U;
+    }
+    if ((flags & FLAGS_LEFT) && minwidth) {
+        // if we're padding on the right, DON'T pad the floating part
+        fwidth = 0U;
+    }
+
+    // rescale the float value
+    if (expval) {
+        value /= conv.F;
+    }
+
+    // output the floating part
+    const size_t start_idx = idx;
+    idx = _ftoa(out, buffer, idx, maxlen, negative ? -value : value, prec, fwidth, flags & ~FLAGS_ADAPT_EXP);
+
+    // output the exponent part
+    if (minwidth) {
+        // output the exponential symbol
+        out((flags & FLAGS_UPPERCASE) ? 'E' : 'e', buffer, idx++, maxlen);
+        // output the exponent value
+        idx = _ntoa_long(out, buffer, idx, maxlen, (expval < 0) ? -expval : expval, expval < 0, 10, 0, minwidth - 1,
+                         FLAGS_ZEROPAD | FLAGS_PLUS);
+        // might need to right-pad spaces
+        if (flags & FLAGS_LEFT) {
+            while (idx - start_idx < width) out(' ', buffer, idx++, maxlen);
+        }
+    }
+    return idx;
+}
+
+#endif  // PRINTF_SUPPORT_EXPONENTIAL
+#endif  // PRINTF_SUPPORT_FLOAT
+
+
+// internal vsnprintf
+static int _vsnprintf(out_fct_type out, char *buffer, const size_t maxlen, const char *format, va_list va) {
+    unsigned int flags, width, precision, n;
+    size_t idx = 0U;
+
+    if (!buffer) {
+        // use null output function
+        out = _out_null;
+    }
+
+    while (*format) {
+        // format specifier?  %[flags][width][.precision][length]
+        if (*format != '%') {
+            // no
+            out(*format, buffer, idx++, maxlen);
+            format++;
+            continue;
+        } else {
+            // yes, evaluate it
+            format++;
+        }
+
+        // evaluate flags
+        flags = 0U;
+        do {
+            switch (*format) {
+                case '0':
+                    flags |= FLAGS_ZEROPAD;
+                    format++;
+                    n = 1U;
+                    break;
+                case '-':
+                    flags |= FLAGS_LEFT;
+                    format++;
+                    n = 1U;
+                    break;
+                case '+':
+                    flags |= FLAGS_PLUS;
+                    format++;
+                    n = 1U;
+                    break;
+                case ' ':
+                    flags |= FLAGS_SPACE;
+                    format++;
+                    n = 1U;
+                    break;
+                case '#':
+                    flags |= FLAGS_HASH;
+                    format++;
+                    n = 1U;
+                    break;
+                default :
+                    n = 0U;
+                    break;
+            }
+        } while (n);
+
+        // evaluate width field
+        width = 0U;
+        if (_is_digit(*format)) {
+            width = _atoi(&format);
+        } else if (*format == '*') {
+            const int w = va_arg(va, int);
+            if (w < 0) {
+                flags |= FLAGS_LEFT;    // reverse padding
+                width = (unsigned int) -w;
+            } else {
+                width = (unsigned int) w;
+            }
+            format++;
+        }
+
+        // evaluate precision field
+        precision = 0U;
+        if (*format == '.') {
+            flags |= FLAGS_PRECISION;
+            format++;
+            if (_is_digit(*format)) {
+                precision = _atoi(&format);
+            } else if (*format == '*') {
+                const int prec = (int) va_arg(va, int);
+                precision = prec > 0 ? (unsigned int) prec : 0U;
+                format++;
+            }
+        }
+
+        // evaluate length field
+        switch (*format) {
+            case 'l' :
+                flags |= FLAGS_LONG;
+                format++;
+                if (*format == 'l') {
+                    flags |= FLAGS_LONG_LONG;
+                    format++;
+                }
+                break;
+            case 'h' :
+                flags |= FLAGS_SHORT;
+                format++;
+                if (*format == 'h') {
+                    flags |= FLAGS_CHAR;
+                    format++;
+                }
+                break;
+#if defined(PRINTF_SUPPORT_PTRDIFF_T)
+            case 't' :
+                flags |= (sizeof(ptrdiff_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
+                format++;
+                break;
+#endif
+            case 'j' :
+                flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
+                format++;
+                break;
+            case 'z' :
+                flags |= (sizeof(size_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
+                format++;
+                break;
+            default :
+                break;
+        }
+
+        // evaluate specifier
+        switch (*format) {
+            case 'd' :
+            case 'i' :
+            case 'u' :
+            case 'x' :
+            case 'X' :
+            case 'o' :
+            case 'b' : {
+                // set the base
+                unsigned int base;
+                if (*format == 'x' || *format == 'X') {
+                    base = 16U;
+                } else if (*format == 'o') {
+                    base = 8U;
+                } else if (*format == 'b') {
+                    base = 2U;
+                } else {
+                    base = 10U;
+                    flags &= ~FLAGS_HASH;   // no hash for dec format
+                }
+                // uppercase
+                if (*format == 'X') {
+                    flags |= FLAGS_UPPERCASE;
+                }
+
+                // no plus or space flag for u, x, X, o, b
+                if ((*format != 'i') && (*format != 'd')) {
+                    flags &= ~(FLAGS_PLUS | FLAGS_SPACE);
+                }
+
+                // ignore '0' flag when precision is given
+                if (flags & FLAGS_PRECISION) {
+                    flags &= ~FLAGS_ZEROPAD;
+                }
+
+                // convert the integer
+                if ((*format == 'i') || (*format == 'd')) {
+                    // signed
+                    if (flags & FLAGS_LONG_LONG) {
+#if defined(PRINTF_SUPPORT_LONG_LONG)
+                        const long long value = va_arg(va, long long);
+                        idx = _ntoa_long_long(out, buffer, idx, maxlen,
+                                              (unsigned long long) (value > 0 ? value : 0 - value), value < 0, base,
+                                              precision, width, flags);
+#endif
+                    } else if (flags & FLAGS_LONG) {
+                        const long value = va_arg(va, long);
+                        idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long) (value > 0 ? value : 0 - value),
+                                         value < 0, base, precision, width, flags);
+                    } else {
+                        const int value = (flags & FLAGS_CHAR) ? (char) va_arg(va, int) : (flags & FLAGS_SHORT)
+                                                                                          ? (short int) va_arg(va, int)
+                                                                                          : va_arg(va, int);
+                        idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int) (value > 0 ? value : 0 - value),
+                                         value < 0, base, precision, width, flags);
+                    }
+                } else {
+                    // unsigned
+                    if (flags & FLAGS_LONG_LONG) {
+#if defined(PRINTF_SUPPORT_LONG_LONG)
+                        idx = _ntoa_long_long(out, buffer, idx, maxlen, va_arg(va, unsigned long long), false, base,
+                                              precision, width, flags);
+#endif
+                    } else if (flags & FLAGS_LONG) {
+                        idx = _ntoa_long(out, buffer, idx, maxlen, va_arg(va, unsigned long), false, base, precision,
+                                         width, flags);
+                    } else {
+                        const unsigned int value = (flags & FLAGS_CHAR) ? (unsigned char) va_arg(va, unsigned int)
+                                                                        : (flags & FLAGS_SHORT)
+                                                                          ? (unsigned short int) va_arg(va,
+                                                                                                        unsigned int)
+                                                                          : va_arg(va, unsigned int);
+                        idx = _ntoa_long(out, buffer, idx, maxlen, value, false, base, precision, width, flags);
+                    }
+                }
+                format++;
+                break;
+            }
+#if defined(PRINTF_SUPPORT_FLOAT)
+            case 'f' :
+            case 'F' :
+                if (*format == 'F') flags |= FLAGS_UPPERCASE;
+                idx = _ftoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
+                format++;
+                break;
+#if defined(PRINTF_SUPPORT_EXPONENTIAL)
+            case 'e':
+            case 'E':
+            case 'g':
+            case 'G':
+                if ((*format == 'g') || (*format == 'G')) flags |= FLAGS_ADAPT_EXP;
+                if ((*format == 'E') || (*format == 'G')) flags |= FLAGS_UPPERCASE;
+                idx = _etoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
+                format++;
+                break;
+#endif  // PRINTF_SUPPORT_EXPONENTIAL
+#endif  // PRINTF_SUPPORT_FLOAT
+            case 'c' : {
+                unsigned int l = 1U;
+                // pre padding
+                if (!(flags & FLAGS_LEFT)) {
+                    while (l++ < width) {
+                        out(' ', buffer, idx++, maxlen);
+                    }
+                }
+                // char output
+                out((char) va_arg(va, int), buffer, idx++, maxlen);
+                // post padding
+                if (flags & FLAGS_LEFT) {
+                    while (l++ < width) {
+                        out(' ', buffer, idx++, maxlen);
+                    }
+                }
+                format++;
+                break;
+            }
+
+            case 's' : {
+                const char *p = va_arg(va, char*);
+                unsigned int l = _strnlen_s(p, precision ? precision : (size_t) -1);
+                // pre padding
+                if (flags & FLAGS_PRECISION) {
+                    l = (l < precision ? l : precision);
+                }
+                if (!(flags & FLAGS_LEFT)) {
+                    while (l++ < width) {
+                        out(' ', buffer, idx++, maxlen);
+                    }
+                }
+                // string output
+                while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
+                    out(*(p++), buffer, idx++, maxlen);
+                }
+                // post padding
+                if (flags & FLAGS_LEFT) {
+                    while (l++ < width) {
+                        out(' ', buffer, idx++, maxlen);
+                    }
+                }
+                format++;
+                break;
+            }
+
+            case 'p' : {
+                width = sizeof(void *) * 2U;
+                flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
+#if defined(PRINTF_SUPPORT_LONG_LONG)
+                const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
+                if (is_ll) {
+                    idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t) va_arg(va, void*), false, 16U,
+                                          precision, width, flags);
+                } else {
+#endif
+                    idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long) ((uintptr_t) va_arg(va, void*)), false,
+                                     16U, precision, width, flags);
+#if defined(PRINTF_SUPPORT_LONG_LONG)
+                }
+#endif
+                format++;
+                break;
+            }
+
+            case '%' :
+                out('%', buffer, idx++, maxlen);
+                format++;
+                break;
+
+            default :
+                out(*format, buffer, idx++, maxlen);
+                format++;
+                break;
+        }
+    }
+
+    // termination
+    out((char) 0, buffer, idx < maxlen ? idx : maxlen - 1U, maxlen);
+
+    // return written chars without terminating \0
+    return (int) idx;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+
+int printf_(const char *format, ...) {
+    va_list va;
+    va_start(va, format);
+    char buffer[1];
+    const int ret = _vsnprintf(_out_char, buffer, (size_t) -1, format, va);
+    va_end(va);
+    return ret;
+}
+
+
+int sprintf_(char *buffer, const char *format, ...) {
+    va_list va;
+    va_start(va, format);
+    const int ret = _vsnprintf(_out_buffer, buffer, (size_t) -1, format, va);
+    va_end(va);
+    return ret;
+}
+
+
+int snprintf_(char *buffer, size_t count, const char *format, ...) {
+    va_list va;
+    va_start(va, format);
+    const int ret = _vsnprintf(_out_buffer, buffer, count, format, va);
+    va_end(va);
+    return ret;
+}
+
+
+int vprintf_(const char *format, va_list va) {
+    char buffer[1];
+    return _vsnprintf(_out_char, buffer, (size_t) -1, format, va);
+}
+
+
+int vsnprintf_(char *buffer, size_t count, const char *format, va_list va) {
+    return _vsnprintf(_out_buffer, buffer, count, format, va);
+}
+
+
+int fctprintf(void (*out)(char character, void *arg), void *arg, const char *format, ...) {
+    va_list va;
+    va_start(va, format);
+    const out_fct_wrap_type out_fct_wrap = {out, arg};
+    const int ret = _vsnprintf(_out_fct, (char *) (uintptr_t) &out_fct_wrap, (size_t) -1, format, va);
+    va_end(va);
+    return ret;
+}