using with strings ? #4
Comments
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Hi, this issue is quite difficult to find a nice solution. However I have come up with a basic workaround. Basically, I have a new type: First though, if you want an array of Before I add this next fix to the lib I want to test it thoroughly, so here is some instructions so you can use it now. Here is the template< unsigned N >
struct cstr_p{
char_p *begin() const{ return (char_p*) &pstr[0];}
char_p *end() const{ return (char_p*) &pstr[N]; }
operator __FlashStringHelper*() const{ return ( __FlashStringHelper* ) &pstr; }
char_p &operator [] (int addr) const{ return *(const char_p*) &pstr[addr]; }
const char pstr[N];
};Then to declare a string, you construct it like this: const cstr_p< 14 > pStr PROGMEM = {"A test String"};Notice the size of the string (including the null) is needed in the template brackets. And the usage is quite straight forward. for( auto &c : pStr ) //Ranged loop over whole string (C++11 only, IDE 1.6.2 and above)
Serial.print( c );
for( int i = 0 ; i < sizeof(pStr) ; ++i ){ //Standard for loop
Serial.print( pStr[i] );
}
Serial.write(pStr[0]); //Print single character
Serial.print(pStr); //Print whole stringAnd here is a complete sketch if you would like to test it. #include <PGMWrap.h>
template< unsigned N >
struct cstr_p{
char_p *begin() const{ return (char_p*) &pstr[0];}
char_p *end() const{ return (char_p*) &pstr[N]; }
operator __FlashStringHelper*() const{ return ( __FlashStringHelper* ) &pstr; }
char_p &operator [] (int addr) const{ return *(const char_p*) &pstr[addr]; }
const char pstr[N];
};
const cstr_p< 14 > pStr PROGMEM = {"A test String"};
void setup() {
Serial.begin(9600);
for( auto &c : pStr ) //Ranged loop over whole string
Serial.print( c );
Serial.write('\n'); //Move to next line
for( int i = 0 ; i < sizeof(pStr) ; ++i ){ //Standard for loop
Serial.print( pStr[i] );
}
Serial.write('\n');
Serial.write(pStr[0]); //Print single character
Serial.write('\n');
Serial.print(pStr); //Print whole string
}
void loop() {}Let me know how you go. Cheers. |
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Hi Chris, I will test your solution and let you know. 2 questions about it:
I got a project here with a very huge menu system (for the GUI) with more than 100 lines of text, my solution up to know is as follows: |
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Hi, this will need some investigation as I have not used UTF-8 within the Arduino environment. However to solve the length problem, use a define for your strings, then you can change the size without having to count each time they change: #define text "Some text"
#define text1 "Some other text "
const cstr_p< sizeof(text) > pStr PROGMEM = {text};
const cstr_p< sizeof(text1) > pStr1 PROGMEM = {text1};I'll investigate other methods, however this should work for now. |
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your example works. but of course counting the size of the string (including the null) is challenging for the user... ;-) using #defines works: using #defines works with UTF-8 as well: |
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Good to hear, You could shrink it to a single line per string with a define if you have many strings. #define createPGMStr( name, text ) const cstr_p< sizeof(text) > name PROGMEM = {text}
createPGMStr( pStr, "some text" );
createPGMStr( pStr1, "some other text" );
createPGMStr( pStr2, "even more text" ); |
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Wow, THAT's what I'm looking for ! I think this is really easy to understand by users of every skill level, So all you have to do is to integrate this in your PGMWrap-library somehow (?) |
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unfortunately my menu example sketch grows from 13000 bytes to 20000 bytes, when using the before: after: |
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I'll have a look and see what is going on. |
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hi cris |
Hi,
how can strings be used with a "PGMWrap-like" style ?
this will not compile
const char_p my_string[] PROGMEM = "my Text";cause of "invalid conversion from 'char*' to 'const char&" issue
the goal is to be able to use strings from flash like any other string (from RAM):
Serial.print(my_string);The text was updated successfully, but these errors were encountered: