String formatting (fmt)

Provides simple string formatting functions.

The goal of this API is to provide a string formatting interface which has a reduced code size footprint compared to the libc provided stdio.h functionality.

This library provides a set of formatting and printing functions for 64 bit integers, even when the C library was built without support for 64 bit formatting (newlib-nano).

Note

The print functions in this library do not buffer any output. Mixing calls to standard printf from stdio.h with the print_xxx functions in fmt, especially on the same output line, may cause garbled output.

msp430_types.h::size_t fmt_byte_hex(char * out, uint8_t byte)

Format a byte value as hex.

E.g., converts byte value 0 to the string 00, 255 to the string FF.

Will write two bytes to out. If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
byte:Byte value to convert

Return values

  • 2
msp430_types.h::size_t fmt_bytes_hex(char * out, const uint8_t * ptr, msp430_types.h::size_t n)

Formats a sequence of bytes as hex bytes.

Will write 2*n bytes to out. If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
ptr:Pointer to bytes to convert
n:Number of bytes to convert

Return values

  • 2*n
msp430_types.h::size_t fmt_bytes_hex_reverse(char * out, const uint8_t * ptr, msp430_types.h::size_t n)

Formats a sequence of bytes as hex bytes, starting with the last byte.

Will write 2*n bytes to out. If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
ptr:Pointer to bytes to convert
n:Number of bytes to convert

Return values

  • 2*n
uint8_t fmt_hex_byte(const char * hex)

Converts a sequence of two hex characters to a byte.

The hex characters sequence must contain valid hexadecimal characters otherwise the result is undefined.

Parameters

hex:Pointer to input buffer

Return values

  • byte based on hex string
msp430_types.h::size_t fmt_hex_bytes(uint8_t * out, const char * hex)

Converts a sequence of hex bytes to an array of bytes.

The sequence of hex characters must have an even length: 2 hex character => 1 byte. If the sequence of hex has an odd length, this function returns 0 and an empty out.

The hex characters sequence must contain valid hexadecimal characters otherwise the result in out is undefined.

Parameters

out:Pointer to converted bytes, or NULL
hex:Pointer to input buffer

Return values

  • strlen(hex) / 2 when length of hex was even
  • 0 otherwise
msp430_types.h::size_t fmt_u16_hex(char * out, uint16_t val)

Convert a uint16 value to hex string.

Will write 4 bytes to out. If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • 4
msp430_types.h::size_t fmt_u32_hex(char * out, uint32_t val)

Convert a uint32 value to hex string.

Will write 8 bytes to out. If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • 8
msp430_types.h::size_t fmt_u64_hex(char * out, uint64_t val)

Convert a uint64 value to hex string.

Will write 16 bytes to out. If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • 16
msp430_types.h::size_t fmt_u32_dec(char * out, uint32_t val)

Convert a uint32 value to decimal string.

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • nr of digits written to (or needed in) out
msp430_types.h::size_t fmt_u64_dec(char * out, uint64_t val)

Convert a uint64 value to decimal string.

If out is NULL, will only return the number of bytes that would have been written.

Note

This adds ~400b of code when used.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • nr of digits written to (or needed in) out
msp430_types.h::size_t fmt_u16_dec(char * out, uint16_t val)

Convert a uint16 value to decimal string.

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • nr of digits written to (or needed in) out
msp430_types.h::size_t fmt_s64_dec(char * out, int64_t val)

Convert a int64 value to decimal string.

Will add a leading “-” if val is negative.

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • nr of characters written to (or needed in) out
msp430_types.h::size_t fmt_s32_dec(char * out, int32_t val)

Convert a int32 value to decimal string.

Will add a leading “-” if val is negative.

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • nr of characters written to (or needed in) out
msp430_types.h::size_t fmt_s16_dec(char * out, int16_t val)

Convert a int16 value to decimal string.

Will add a leading “-” if val is negative.

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
val:Value to convert

Return values

  • nr of characters written to (or needed in) out
msp430_types.h::size_t fmt_s16_dfp(char * out, int16_t val, int fp_digits)

Convert 16-bit fixed point number to a decimal string.

See fmt.h::fmt_s32_dfp() for more details

Parameters

out:Pointer to the output buffer, or NULL
val:Fixed point value
fp_digits:Number of digits after the decimal point, MUST be >= -7

Return values

  • Length of the resulting string
msp430_types.h::size_t fmt_s32_dfp(char * out, int32_t val, int fp_digits)

Convert 32-bit fixed point number to a decimal string.

The input for this function is a signed 32-bit integer holding the fixed point value as well as an integer defining the position of the decimal point. This value is used to shift the decimal point to the right (positive value of fp_digits) or to the left (negative value of fp_digits).

Will add a leading “-” if val is negative.

The resulting string will always be patted with zeros after the decimal point.

For example: if val is -3548 and fp_digits is -2, the resulting string will be “-35.48”. The same value for val with fp_digits of 2 will result in “-354800”.

Parameters

out:Pointer to the output buffer, or NULL
val:Fixed point value
fp_digits:Number of digits after the decimal point, MUST be >= -7

Return values

  • Length of the resulting string
msp430_types.h::size_t fmt_float(char * out, float f, unsigned precision)

Format float to string.

Converts float value f to string

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:string to write to (or NULL)
f:float value to convert
precision:number of digits after decimal point

Return values

  • nr of bytes the function did or would write to out
msp430_types.h::size_t fmt_char(char * out, char c)

Copy in char to string (without terminating ‘\0’)

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:string to write to (or NULL)
c:char value to append

Return values

  • nr of bytes the function did or would write to out
msp430_types.h::size_t fmt_strlen(const char * str)

Count characters until ‘\0’ (exclusive) in str.

Parameters

str:Pointer to string

Return values

  • nr of characters in string str points to
msp430_types.h::size_t fmt_strnlen(const char * str, msp430_types.h::size_t maxlen)

Count at most maxlen characters until ‘\0’ (exclusive) in str.

Parameters

str:Pointer to string
maxlen:Maximum number of chars to count

Return values

  • nr of characters in string str points to, or maxlen if no null terminator is found within maxlen chars
msp430_types.h::size_t fmt_str(char * out, const char * str)

Copy null-terminated string (excluding terminating \0)

If out is NULL, will only return the number of bytes that would have been written.

Parameters

out:Pointer to output buffer, or NULL
str:Pointer to null-terminated source string

Return values

  • nr of characters written to (or needed in) out
msp430_types.h::size_t fmt_to_lower(char * out, const char * str)

Copy null-terminated string to a lowercase string (excluding terminating \0)

Parameters

out:Pointer to output buffer, or NULL
str:Pointer to null-terminated source string

uint32_t scn_u32_dec(const char * str, msp430_types.h::size_t n)

Convert digits to uint32.

Will convert up to n digits. Stops at any non-digit or ‘\0’ character.

Parameters

str:Pointer to string to read from
n:Maximum nr of characters to consider

Return values

  • converted uint32_t value
uint32_t scn_u32_hex(const char * str, msp430_types.h::size_t n)

Convert hexadecimal characters to uin32_t.

Will convert up to n char. Stop at any non-hexadecimal or ‘\0’ character

Parameters

str:Pointer to tring to read from
n:Maximum number of characters to consider

Return values

  • converted uint32_t value
void print(const char * s, msp430_types.h::size_t n)

Print string to stdout.

Writes n bytes from s to STDOUT_FILENO.

Parameters

s:Pointer to string to print
n:Number of bytes to print

void print_u32_dec(uint32_t val)

Print uint32 value to stdout.

Parameters

val:Value to print

void print_s32_dec(int32_t val)

Print int32 value to stdout.

Parameters

val:Value to print

void print_byte_hex(uint8_t byte)

Print byte value as hex to stdout.

Parameters

byte:Byte value to print

void print_u32_hex(uint32_t val)

Print uint32 value as hex to stdout.

Parameters

val:Value to print

void print_u64_hex(uint64_t val)

Print uint64 value as hex to stdout.

Parameters

val:Value to print

void print_u64_dec(uint64_t val)

Print uint64 value as decimal to stdout.

Note

This uses fmt.h::fmt_u64_dec(), which uses ~400b of code.

Parameters

val:Value to print

void print_float(float f, unsigned precision)

Print float value.

Note

See fmt_float for code size warning!

Parameters

f:float value to print
precision:number of digits after decimal point

void print_str(const char * str)

Print null-terminated string to stdout.

Parameters

str:Pointer to string to print

msp430_types.h::size_t fmt_lpad(char * str, msp430_types.h::size_t in_len, msp430_types.h::size_t pad_len, char pad_char)

Pad string to the left.

This function left-pads a given string str with pad_char.

For example, calling

would result in ” abcd”.

The function only writes to str if str is non-NULL and pad_len is < in_len.

Note

Caller must ensure str can take pad_len characters!

Parameters

str:string to pad (or NULL)
in_len:length of str
pad_len:total length after padding
pad_char:char to use as pad char

Return values

  • max(in_len, pad_len)
FMT_USE_MEMMOVE

use memmove() or internal implementation 

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