1. Macro substitution library ----------------------------- This library could be used directly by applications which need to support macro substitution. It will be implemented on all platforms. 1.1 Core library ---------------- The core library provides a minimal set of basic operations. Some utility routines, described later, use core routines to provide a more convenient interface for some purposes. a) long macCreateHandle( MAC_HANDLE **handle, char *pairs[] ); void macSuppressWarning(MAC_HANDLE *handle,int falseTrue); Creates a new macro substitution context and returns an opaque handle to that context. An application can, if it desires, have several active contexts, although most will not. If desired, an initial set of macro definitions may be loaded ("pairs" is set to NULL to avoid this). The definitions are in the "standard" pairs format, as described under macParseDefns(). Note that MAC_HANDLE is a typedef for the context structure. The opaque handle is of type "MAC_HANDLE *", which is a pointer to the context structure. The memory for this context is allocated by this routine. macSuppressWarning can be called to suppress the marning message when macExpandString cant expand a macro. A non zero value will suppress the messages. c) long macGetValue ( MAC_HANDLE *handle, char *name, char *value, long maxlen ); Returns up to maxlen characters of the value of macro "name". "value" will be zero-terminated if the length of the value is less than maxlen. The function value will be the number of characters copied to "value" (see below for behavior if the macro is undefined). If maxlen is zero, no characters will be copied to "value" (which can be NULL) and the call can be used to check whether the macro is defined. Note that truncation of the value is therefore not reported. Is this a problem? If the macro is undefined, the macro reference will be returned in the value string (if permitted by maxlen) and the function value will be _minus_ the number of characters copied. Note that treatment of maxlen is intended to be consistent with what people are used to with strncpy(). If the value contains macro references then the references will be expanded recursively. This expansion will detect a direct or indirect self reference. Macro references begin with a "$" immediately followed by either a "(" or a "{" character. The macro name comes next, and may optionally be succeeded by an "=" and a default value, which will be returned if the named macro is undefined at the moment of expansion. The reference is terminated by the matching ")" or "}" character. d) long macPutValue( MAC_HANDLE *handle, char *name, char *value ); Sets the value of the macro "name". If "value" is NULL, it undefines all instances of "name" at all scoping levels (it's not an error if "name" is not defined in this case). Macros referenced by "value" need not be defined at this point. The function returns the length of the value string. e) long macDeleteHandle( MAC_HANDLE *handle ); Marks a handle invalid, and frees all storage associated with it. Note that this does not free any strings into which macro values have been returned. Macro values are always returned into strings which were pre-allocated by the caller. f) long macPushScope( MAC_HANDLE *handle ); Marks the start of a new scoping level such that all definitions made up until the next macPopScope() call will be lost on macPopScope() and those current at macPushScope() will be re-instated. g) long macPopScope( MAC_HANDLE *handle ); See macPushScope. h) Error handling These routines conform to 0 (=OK) for success, -1 (=ERROR) for failure, and small positive values for extra info. I contravened this for macGetValue() and macExpandString() because I felt that it was worth returning information both on success / failure and on value length. Errors and warnings are reported using errlogPrintf(). 1.2 Utility library ------------------- These are convenience functions. If other useful functions emerge during implementation, the list may grow. a) macParseDefns( MAC_HANDLE *handle, char *defns, char **pairs[] ); This takes a set of macro definitions in "a=xxx,b=yyy" format and converts them into an array of pointers to character strings which are, in order, "first name", "first value", "second name", "second value" etc. The array is terminated with two NULL pointers and all storage is allocated contiguously so that it can be freed with a single call to free(). This routine is independent of any handle and provides a generally useful service which may be used elsewhere. Any macro references in values are not expanded at this point since the referenced macros may be defined or redefined before the macro actually has to be translated. Shell-style escapes and quotes are supported, as are things like "A=B,B=$(C$(A)),CA=CA,CB=CB" (sets B to "CB"). White space is significant within values but ignored elsewhere (i.e. surrounding "=" and "," characters). Probably noone will ever want to, but the special meanings of "$", "{", "}", "(", ")", "=" and "," can all be changed via macPutXxxx() calls. This routine does not have a handle argument, so they must be changed globally for it to use the new definitions. Should it have a handle argument? This makes it more of a pain to use but guarantees that there will be no conflicts. I think it should really. The function value is the number of definitions encountered, or -1 if the supplied string is invalid. b) long macInstallMacros( MAC_HANDLE *handle, char *pairs[] ); This takes an array of pairs as defined above and installs them as definitions by calling macPutValue(). The pairs array is terminated by a NULL pointer. The function value is the number of macros defined. c) long macExpandString( MAC_HANDLE *handle, char *src, char *dest, long maxlen ); This operates on a string which may contain macro references. It parses the string looking for such references and passes them to macGetValue() for translation. It returns the expanded string in the supplied argument. The function value is similar to that of macGetValue(). Its absolute value is the number of characters copied. If negative, at least one undefined macro has been left unexpanded. d) char *macEnvExpand( char *src ); This operates on a string which may contain macros defined by environment variables. It parses the string looking for such references and passes them to macGetValue() for translation. It uses malloc() to allocate space for the expanded string and returns a pointer to this null-terminated string. It returns NULL if the source string contains any undefined references. e) long macReportMacros( MAC_HANDLE *handle ); This reports details of current definitions to standard output, and is intended purely for debugging purposes.