mwx::stream

input-output stream

Upper-level class that handles input/output streams.

  • Interfaces to several classes (Serial, Wire, SPI, smplbuf) by polymorphism using CRTP (Curiously Recurring Template Pattern) method.

    • In CRTP, lower classes are defined as template class Derived : public stream<Derived>; and methods of lower classes are referenced from upper classes.

  • This class defines common processing such as print method, << operator, etc., and calls write() method, etc. implemented in lower classes, which is similar to using virtual functions.

Interfaces (implemented in lower classes)

Lower classes implement the functions listed below.

available()

int available()

// example
while(Serial.available()) {
  int c = Serial.read();
  // ... any
}

Returns 1 if the input exists, 0 if it does not.

Parameters
Description

Return value int

0: no data 1: data present

The return value of this implementation is not the buffer length.

flush()

void flush()

// example
Serial.println("long long word .... ");
Serial.flush();

Flush output (wait for output to complete).

read()

int read()

// example
int c;
while (-1 != (c = read())) {
    // any
}

Inputs 1-byte data from the stream. If the data does not exist, return -1.

write()

size_t write(int c)

// example
Serial.write(0x30);

Outputs 1 byte to the stream.

Parameters
Description

n

The character you want to output.

Return value size_t

1 if output succeeds, 0 if it fails.

vOutput()

static void vOutput(char out, void* vp)

This is a static function that produces a single byte output. Since this is not a class method, member variables and other information are not available. Instead, a pointer to the class instance is passed to vp, which is passed as a parameter.

This static function is used internally and the function pointer is passed as a one-byte output function of fctprintf(). This is used to implement the print method, etc.

Parameters
Description

out

the character to output

vp

pointer to a class instance Usually, cast to the original class and call the write() method

Interface

putchar()

void mwx::stream::putchar(char c)

// example
Serial.putchar('A');
// result -> A

Output a single byte.

print(), println()

size_t print(T val, int base = DEC) // T: 整数型
size_t print(double val, int place = 2)
size_t print(const char*str)
size_t print(std::initializer_list<int>)

// example
Serial.print("the value is ");
Serial.print(123, DEC);
Serial.println(".");
// result -> the value is 123.

Serial.print(123.456, 1);
// result -> 123.5

Serial.print({ 0x12, 0x34, 0xab, 0xcd });
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Performs various types of formatted output.

Paramita
Explanation

val

Integer powerups

base

power form BIN binary / OCT 8 math / DEC 10 math / HEX 16 math

place

Number of decimals below the decimal point

back size_t

the number of booklets

printfmt()

size_t printfmt(const char* format, ...);

// example 
Serial.printfmt("the value is %d.", 123);
// result -> the value is 123.

Prints output in printf format.

TWESDK/TWENET/current/src/printf/README.md 参照

operator <<

// examples
Serial << "this value is" // const char*
       << int(123)
       << '.';
       << mwx::crlf;
// result -> this value is 123.

Serial << fromat("this value is %d.", 123) << twe::crlf;
// result -> this value is 123.

Serial << mwx::flush; // flush here

Serial << bigendian(0x1234abcd);
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Serial << int(0x30) // output 0x30=48, "48"
       << '/'
       << uint8_t(0x31); // output '1', not "48"
// result -> 48/1

smplbuf<char,16> buf = { 0x12, 0x34, 0xab, 0xcd };
Serail << but.to_stream();
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Seiral << make_pair(buf.begin(), buf.end());
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Serial << bytelist({ 0x12, 0x34, 0xab, 0xcd });
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.
Argument type
Explanation

char

1-byte output (not formatted as a number)

1-byte output (not formatted as a number)

double

numeric output (printf's "%.2f")

uint8_t

output 1 byte (same as char type)

uint16_t

output 2 bytes (big-endian order)

uint32_t

output 4 bytes (big-endian order)

const char* uint8_t* const char[S]

Output up to the terminating character. Output does not include the terminating character. >(S specifies the size of the fixed array)

uint8_t[S]

Output the array size S bytes as is. (S is the fixed array size specification)

format()

output in printf format

mwx::crlf

output of newline CRLF

mwx::flush

flush output

bigendian()

output numeric types in big-endian order. (right-hand side value)

std::pair<T*, T*>

A pair containing begin(), end() pointers of byte type. Can be created by make_pair. Tis assumed to be of typeuint8_t`. (right-hand side value)

output byte string using bytelist()

std::initializer_list.

smplbuf<uint8_t,AL>&

Output the contents of an array class of type uint8_t. ALC is memory allocation method.

smplbuf<uint8_t, AL>::to_stream()

Outputs data of smplbuf&#x3C;T> T is of type uint8_t, AL is a memory allocation method.

When outputting as a byte string, cast to uint8_t, uint16_t, uint32_t type. When outputting numerical values as strings, explicitly cast to int type.

Single-byte types are handled differently depending on the type name. Usually, use the size-conscious uint8_t[S] type.

set_timeout(), get_error_status(), clear_error_status()

uint8_t get_error_status()
void clear_error_status()
void set_timeout(uint8_t centisec)

// example
Serial.set_timeout(100); // 1000msのタイムアウトを設定
uint8_t c;
Serial >> c;

Manages input timeouts and errors using the >> operator.

The timeout period is specified by set_timeout(), and input is processed using the >> operator. If no input is received within the given timeout period, the error value can be read out with get_error_status(). The error status is cleared by clear_error_status().

Argument type
Description

centisec

Sets the timeout period in units of 1/10 second. If 0xff is specified, timeout is disabled.

Error Value

Value
Meaning

0

No Error

1

Error Status

operator >>

inline D& operator >> (uint8_t& v)
inline D& operator >> (char_t& v)
template <int S> inline D& operator >> (uint8_t(&v)[S])
inline D& operator >> (uint16_t& v)
inline D& operator >> (uint32_t& v)
inline D& operator >> (mwx::null_stream&& p)

//// Example
uint8_t c;

the_twelite.stop_watchdog(); // stop watchdog
Serial.set_timeout(0xFF); // no timeout

// read out 1 byte
Serial >> c;
Serial << crlf << "char #1: [" << c << ']';

// skipping
Serial >> null_stream(3); // Read away 3 bytes
Serial << crlf << "char #2-4: skipped";

// Read 4 bytes (limited to fixed-length arrays of type uint8_t)
uint8_t buff[4];
Serial >> buff;
Serial << crlf << "char #5-8: [" << buff << "]";

Input processing.

  • Cannot be executed within setup().

  • Because it waits for polling, depending on the timeout time setting (e.g. no timeout), the watchdog timer may be triggered and reset.

Normally, the following readout is performed during loop().

void loop() {
  uint8_t c;
  while(Serial.available()) {
    Serial >> c;
    // Or c = Serial.read();
    
    switch(c) { ... }  // Branch processing according to the value of c
  }
}

The following is a list of types that can be read and stored.

Argument type
Explanation

1-byte input (big-endian order)

2-byte input (big-endian order)

uint32_t

4-byte input (big-endian order)

uint8_t[S]

input for S bytes (S specifies fixed array size)

null_stream(int n)

read n bytes away

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