diff options
Diffstat (limited to 'pod/perlembed.pod')
| -rw-r--r-- | pod/perlembed.pod | 105 |
1 files changed, 38 insertions, 67 deletions
diff --git a/pod/perlembed.pod b/pod/perlembed.pod index 9e3fb5250a..79783a7d30 100644 --- a/pod/perlembed.pod +++ b/pod/perlembed.pod @@ -263,57 +263,49 @@ your C program>. =head2 Evaluating a Perl statement from your C program -One way to evaluate pieces of Perl code is to use -L<perlguts/perl_eval_sv()>. We've wrapped this inside our own -I<perl_eval()> function, which converts a command string to an SV, -passing this and the L<perlcall/G_DISCARD> flag to -L<perlguts/perl_eval_sv()>. - -Arguably, this is the only routine you'll ever need to execute -snippets of Perl code from within your C program. Your string can be +Perl provides two API functions to evaluate pieces of Perl code. +These are L<perlguts/perl_eval_sv()> and L<perlguts/perl_eval_pv()>. + +Arguably, these are the only routines you'll ever need to execute +snippets of Perl code from within your C program. Your code can be as long as you wish; it can contain multiple statements; it can employ L<perlfunc/use>, L<perlfunc/require> and L<perlfunc/do> to include external Perl files. -Our I<perl_eval()> lets us evaluate individual Perl strings, and then +I<perl_eval_pv()> lets us evaluate individual Perl strings, and then extract variables for coercion into C types. The following program, I<string.c>, executes three Perl strings, extracting an C<int> from the first, a C<float> from the second, and a C<char *> from the third. #include <EXTERN.h> #include <perl.h> - + static PerlInterpreter *my_perl; - - I32 perl_eval(char *string) - { - return perl_eval_sv(newSVpv(string,0), G_DISCARD); - } - + main (int argc, char **argv, char **env) { - char *embedding[] = { "", "-e", "0" }; - STRLEN length; - - my_perl = perl_alloc(); - perl_construct( my_perl ); - - perl_parse(my_perl, NULL, 3, embedding, NULL); - perl_run(my_perl); - /** Treat $a as an integer **/ - perl_eval("$a = 3; $a **= 2"); - printf("a = %d\n", SvIV(perl_get_sv("a", FALSE))); - - /** Treat $a as a float **/ - perl_eval("$a = 3.14; $a **= 2"); - printf("a = %f\n", SvNV(perl_get_sv("a", FALSE))); - - /** Treat $a as a string **/ - perl_eval("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a); "); - printf("a = %s\n", SvPV(perl_get_sv("a", FALSE), length)); - - perl_destruct(my_perl); - perl_free(my_perl); + char *embedding[] = { "", "-e", "0" }; + + my_perl = perl_alloc(); + perl_construct( my_perl ); + + perl_parse(my_perl, NULL, 3, embedding, NULL); + perl_run(my_perl); + + /** Treat $a as an integer **/ + perl_eval_pv("$a = 3; $a **= 2", TRUE); + printf("a = %d\n", SvIV(perl_get_sv("a", FALSE))); + + /** Treat $a as a float **/ + perl_eval_pv("$a = 3.14; $a **= 2", TRUE); + printf("a = %f\n", SvNV(perl_get_sv("a", FALSE))); + + /** Treat $a as a string **/ + perl_eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); + printf("a = %s\n", SvPV(perl_get_sv("a", FALSE), na)); + + perl_destruct(my_perl); + perl_free(my_perl); } All of those strange functions with I<sv> in their names help convert Perl scalars to C types. They're described in L<perlguts>. @@ -329,28 +321,10 @@ I<SvPV()> to create a string: In the example above, we've created a global variable to temporarily store the computed value of our eval'd expression. It is also possible and in most cases a better strategy to fetch the return value -from L<perl_eval_sv> instead. Example: - - SV *perl_eval(char *string, int croak_on_error) - { - dSP; - SV *sv = newSVpv(string,0); +from L<perl_eval_pv> instead. Example: - PUSHMARK(sp); - perl_eval_sv(sv, G_SCALAR); - SvREFCNT_dec(sv); - - SPAGAIN; - sv = POPs; - PUTBACK; - - if (croak_on_error && SvTRUE(GvSV(errgv))) - croak(SvPV(GvSV(errgv),na)); - - return sv; - } ... - SV *val = perl_eval("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); + SV *val = perl_eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); printf("%s\n", SvPV(val,na)); ... @@ -359,7 +333,7 @@ variables and we've simplified our code as well. =head2 Performing Perl pattern matches and substitutions from your C program -Our I<perl_eval()> lets us evaluate strings of Perl code, so we can +The I<perl_eval_pv()> function lets us evaluate strings of Perl code, so we can define some functions that use it to "specialize" in matches and substitutions: I<match()>, I<substitute()>, and I<matches()>. @@ -390,10 +364,7 @@ been wrapped here): #include <perl.h> static PerlInterpreter *my_perl; - I32 perl_eval(char *string) - { - return perl_eval_sv(newSVpv(string,0), G_DISCARD); - } + /** match(string, pattern) ** ** Used for matches in a scalar context. @@ -406,7 +377,7 @@ been wrapped here): command = malloc(sizeof(char) * strlen(string) + strlen(pattern) + 37); sprintf(command, "$string = '%s'; $return = $string =~ %s", string, pattern); - perl_eval(command); + perl_eval_pv(command, TRUE); free(command); return SvIV(perl_get_sv("return", FALSE)); } @@ -424,7 +395,7 @@ been wrapped here): command = malloc(sizeof(char) * strlen(*string) + strlen(pattern) + 35); sprintf(command, "$string = '%s'; $ret = ($string =~ %s)", *string, pattern); - perl_eval(command); + perl_eval_pv(command, TRUE); free(command); *string = SvPV(perl_get_sv("string", FALSE), length); return SvIV(perl_get_sv("ret", FALSE)); @@ -447,7 +418,7 @@ been wrapped here): command = malloc(sizeof(char) * strlen(string) + strlen(pattern) + 38); sprintf(command, "$string = '%s'; @array = ($string =~ %s)", string, pattern); - perl_eval(command); + perl_eval_pv(command, TRUE); free(command); array = perl_get_av("array", FALSE); num_matches = av_len(array) + 1; /** assume $[ is 0 **/ @@ -990,7 +961,7 @@ Dov Grobgeld, and Ilya Zakharevich. Check out Doug's article on embedding in Volume 1, Issue 4 of The Perl Journal. Info about TPJ is available from http://tpj.com. -February 1, 1997 +April 14, 1997 Some of this material is excerpted from Jon Orwant's book: I<Perl 5 Interactive>, Waite Group Press, 1996 (ISBN 1-57169-064-6) and appears |