Difference between revisions of "Multi language C embedded"
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In this small example both languages are in the same file. In a project, you should have a file called english.h where all your english messages should reside. When the project is internationalized send a copy of english.h to the translator with a new name. For example german.h | In this small example both languages are in the same file. In a project, you should have a file called english.h where all your english messages should reside. When the project is internationalized send a copy of english.h to the translator with a new name. For example german.h | ||
| − | '''Remember:''' The translator must keep the variables as indicated by %<TYPE> in all messages. | + | '''Remember:''' The translator must keep the variables as indicated by %<TYPE> in all messages, in the same order. |
<source lang=c> | <source lang=c> | ||
char const * const danish[] = { | char const * const danish[] = { | ||
| Line 41: | Line 41: | ||
</source> | </source> | ||
The drawback of this method is that the array-members need to come in this exact order and if you delete one of the members, it’s necessary to leave an empty (“”) string as the array-member number is the reference to the string when used. For example textmes(2) references the battery warning. | The drawback of this method is that the array-members need to come in this exact order and if you delete one of the members, it’s necessary to leave an empty (“”) string as the array-member number is the reference to the string when used. For example textmes(2) references the battery warning. | ||
| + | |||
== Using array initialization with enum indices == | == Using array initialization with enum indices == | ||
It is possible to initialize arrays – even const arrays – referencing members at compiletime. | It is possible to initialize arrays – even const arrays – referencing members at compiletime. | ||
<source lang=c> | <source lang=c> | ||
| − | enum | + | enum texts { |
ERR_NONEXCOM = 0, | ERR_NONEXCOM = 0, | ||
ERR_INVDATE, | ERR_INVDATE, | ||
ERR_LOWBAT, | ERR_LOWBAT, | ||
| − | } | + | } ; |
char const * const danish[] = { | char const * const danish[] = { | ||
Latest revision as of 07:43, 27 March 2021
Different approaches of implementing multi language support in embedded C projects. (See links below).
Design goals
- Should only exist in flash. (No copying to RAM)
- Logical for translators to translate from english to other language.
- Easy to change language on-the-fly
- No padding of strings to max length in arrays
- In the example below the text strings yes and no use the same amount of memory as the long message and will be copied to RAM on a system with firmware.
char txt[3][] = {
"Yes",
"No",
"The format received is inconsistent with RFC 1024",
};
Simple Example
In this small example both languages are in the same file. In a project, you should have a file called english.h where all your english messages should reside. When the project is internationalized send a copy of english.h to the translator with a new name. For example german.h
Remember: The translator must keep the variables as indicated by %<TYPE> in all messages, in the same order.
char const * const danish[] = {
"FEJL: Kommando eksisterer ikke: %s",
"FEJL: Dato %s ugyldig",
"Advarsel: Der er kun %u%% batteri tilbage!"
};
char const * const english[] = {
"ERROR: Non-existing command: %s",
"ERROR: Invalid Date %s",
"Warning: Only %u%% battery left!"
};
void example(void) {
char **textmes;
textmes = (char **) &danish; // Set danish language
printf( textmes[2], 17); // Outputs: Advarsel: Der er kun 17% batteri tilbage!
textmes = (char **) &english; // Set english language
printf( textmes[2], 17); // Outputs: Warning: Only 17% battery left!
}
The drawback of this method is that the array-members need to come in this exact order and if you delete one of the members, it’s necessary to leave an empty (“”) string as the array-member number is the reference to the string when used. For example textmes(2) references the battery warning.
Using array initialization with enum indices
It is possible to initialize arrays – even const arrays – referencing members at compiletime.
enum texts {
ERR_NONEXCOM = 0,
ERR_INVDATE,
ERR_LOWBAT,
} ;
char const * const danish[] = {
[ERR_NONEXCOM] = "FEJL: Kommando eksisterer ikke: %s",
[ERR_INVDATE] = "FEJL: Dato %s ugyldig",
[ERR_LOWBAT] = "Advarsel: Der er kun %u%% batteri tilbage!"
};
char const * const english[] = {
[ERR_NONEXCOM] = "ERROR: Non-existing command: %s",
[ERR_INVDATE] = "ERROR: Invalid Date %s",
[ERR_LOWBAT] = "Warning: Only %u%% battery left!"
};
void example(void) {
char **textmes;
int i;
textmes = (char **) &english; // Set english language
printf( textmes[ERR_LOWBAT], 17); // Outputs: Warning: Only 17% battery left!
textmes = (char **) &danish; // Set danish language
printf( textmes[ERR_LOWBAT], 17); // Outputs: Advarsel: Der er kun 17% batteri tilbage!
}