X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlguts.pod;h=d93eadf2ef504cd7364aa37f771c2b79daf5279c;hb=351f32542342b92f7303dec0a812c5301714120f;hp=2b8faf007f00840e161fecc6d275561ddd14c309;hpb=fe854a6f990f7776a8ee8bd28f02e1bd36e5bb58;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlguts.pod b/pod/perlguts.pod index 2b8faf0..d93eadf 100644 --- a/pod/perlguts.pod +++ b/pod/perlguts.pod @@ -29,24 +29,34 @@ Additionally, there is the UV, which is simply an unsigned IV. Perl also uses two special typedefs, I32 and I16, which will always be at least 32-bits and 16-bits long, respectively. (Again, there are U32 and U16, -as well.) +as well.) They will usually be exactly 32 and 16 bits long, but on Crays +they will both be 64 bits. =head2 Working with SVs -An SV can be created and loaded with one command. There are four types of -values that can be loaded: an integer value (IV), a double (NV), -a string (PV), and another scalar (SV). +An SV can be created and loaded with one command. There are five types of +values that can be loaded: an integer value (IV), an unsigned integer +value (UV), a double (NV), a string (PV), and another scalar (SV). -The six routines are: +The seven routines are: SV* newSViv(IV); + SV* newSVuv(UV); SV* newSVnv(double); SV* newSVpv(const char*, int); SV* newSVpvn(const char*, int); SV* newSVpvf(const char*, ...); SV* newSVsv(SV*); -To change the value of an *already-existing* SV, there are seven routines: +If you require more complex initialisation you can create an empty SV with +newSV(len). If C is 0 an empty SV of type NULL is returned, else an +SV of type PV is returned with len + 1 (for the NUL) bytes of storage +allocated, accessible via SvPVX. In both cases the SV has value undef. + + SV* newSV(0); /* no storage allocated */ + SV* newSV(10); /* 10 (+1) bytes of uninitialised storage allocated */ + +To change the value of an *already-existing* SV, there are eight routines: void sv_setiv(SV*, IV); void sv_setuv(SV*, UV); @@ -54,7 +64,7 @@ To change the value of an *already-existing* SV, there are seven routines: void sv_setpv(SV*, const char*); void sv_setpvn(SV*, const char*, int) void sv_setpvf(SV*, const char*, ...); - void sv_vsetpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool); + void sv_vsetpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool *); void sv_setsv(SV*, SV*); Notice that you can choose to specify the length of the string to be @@ -599,10 +609,25 @@ be set, using the routines appropriate to the data type. There are additional macros whose values may be bitwise OR'ed with the C argument to enable certain extra features. Those bits are: - GV_ADDMULTI Marks the variable as multiply defined, thus preventing the - "Name used only once: possible typo" warning. - GV_ADDWARN Issues the warning "Had to create unexpectedly" if - the variable did not exist before the function was called. +=over + +=item GV_ADDMULTI + +Marks the variable as multiply defined, thus preventing the: + + Name used only once: possible typo + +warning. + +=item GV_ADDWARN + +Issues the warning: + + Had to create unexpectedly + +if the variable did not exist before the function was called. + +=back If you do not specify a package name, the variable is created in the current package. @@ -674,7 +699,7 @@ The first call creates a mortal SV (with no value), the second converts an exist SV to a mortal SV (and thus defers a call to C), and the third creates a mortal copy of an existing SV. Because C gives the new SV no value,it must normally be given one -via C, C etc. : +via C, C, etc. : SV *tmp = sv_newmortal(); sv_setiv(tmp, an_integer); @@ -833,7 +858,7 @@ SV. The C and C arguments are used to associate a string with the magic, typically the name of a variable. C is stored in the -C field and if C is non-null and C >= 0 a malloc'd +C field and if C is non-null and C E= 0 a malloc'd copy of the name is stored in C field. The sv_magic function uses C to determine which, if any, predefined @@ -843,7 +868,7 @@ stored in the C field. The value of C should be chosen from the set of macros C found perl.h. Note that before these macros were added, Perl internals used to directly use character literals, so you may occasionally come across old code or documentation -referrring to 'U' magic rather than C for example. +referring to 'U' magic rather than C for example. The C argument is stored in the C field of the C structure. If it is not the same as the C argument, the reference @@ -886,7 +911,7 @@ actions depending on which function is being called. Function pointer Action taken ---------------- ------------ - svt_get Do something after the value of the SV is retrieved. + svt_get Do something before the value of the SV is retrieved. svt_set Do something after the SV is assigned a value. svt_len Report on the SV's length. svt_clear Clear something the SV represents. @@ -1034,7 +1059,7 @@ you find yourself actually applying such information in this section, be aware that the behavior may change in the future, umm, without warning. The perl tie function associates a variable with an object that implements -the various GET, SET etc methods. To perform the equivalent of the perl +the various GET, SET, etc methods. To perform the equivalent of the perl tie function from an XSUB, you must mimic this behaviour. The code below carries out the necessary steps - firstly it creates a new hash, and then creates a second hash which it blesses into the class which will implement @@ -1128,7 +1153,7 @@ This construction is I equivalent to The biggest difference is that the first construction would reinstate the initial value of $var, irrespective of how control exits -the block: C, C, C/C etc. It is a little bit +the block: C, C, C/C, etc. It is a little bit more efficient as well. There is a way to achieve a similar task from C via Perl API: create a @@ -1342,7 +1367,7 @@ trapped, and how to treat return values. All four routines return the number of arguments that the subroutine returned on the Perl stack. -These routines used to be called C etc., before Perl v5.6.0, +These routines used to be called C, etc., before Perl v5.6.0, but those names are now deprecated; macros of the same name are provided for compatibility. @@ -1490,7 +1515,7 @@ the scratchpad AV. In fact it contains a pointer to an AV of (initially) one element, and this element is the scratchpad AV. Why do we need an extra level of indirection? -The answer is B, and maybe (sometime soon) B. Both +The answer is B, and maybe B. Both these can create several execution pointers going into the same subroutine. For the subroutine-child not write over the temporaries for the subroutine-parent (lifespan of which covers the call to the @@ -1731,7 +1756,7 @@ interpreters, with one interpreter represented either as a C structure, or inside a thread-specific structure. These structures contain all the context, the state of that interpreter. -Three macros control the major Perl build flavors: MULTIPLICITY, and +Two macros control the major Perl build flavors: MULTIPLICITY and USE_5005THREADS. The MULTIPLICITY build has a C structure that packages all the interpreter state, and there is a similar thread-specific data structure under USE_5005THREADS. In both cases, @@ -2342,7 +2367,7 @@ high character - C is one of those. =head1 Custom Operators -Custom operator support is a new experimental feature that allows you do +Custom operator support is a new experimental feature that allows you to define your own ops. This is primarily to allow the building of interpreters for other languages in the Perl core, but it also allows optimizations through the creation of "macro-ops" (ops which perform the @@ -2386,15 +2411,15 @@ the Perl interpreter. =head1 AUTHORS Until May 1997, this document was maintained by Jeff Okamoto -. It is now maintained as part of Perl itself -by the Perl 5 Porters . +Eokamoto@corp.hp.comE. It is now maintained as part of Perl +itself by the Perl 5 Porters Eperl5-porters@perl.orgE. With lots of help and suggestions from Dean Roehrich, Malcolm Beattie, Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer, Stephen McCamant, and Gurusamy Sarathy. -API Listing originally by Dean Roehrich . +API Listing originally by Dean Roehrich Eroehrich@cray.comE. Modifications to autogenerate the API listing (L) by Benjamin Stuhl.