64 lines
2.3 KiB
C
64 lines
2.3 KiB
C
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/*
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* tcldir.h --
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*
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* Resolve magic's Tcl-runtime directory (where magic.tcl, tclmagic.so, and the
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* Tcl auto_path packages live) at *run time* instead of hardwiring the
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* compile-time install path.
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*
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* If the environment variable CAD_ROOT is set and non-empty, use
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* $CAD_ROOT/magic/tcl -- so magic runs from a relocated install, or straight out
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* of a build tree (via a staged CAD_ROOT), the same way the sys files already
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* follow CAD_ROOT and the tcltk/magic.sh wrapper already computes
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* TCL_MAG_DIR=${CAD_ROOT}/magic/tcl. Otherwise fall back to the compile-time
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* TCL_DIR (the default install location).
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*
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* Must be included in a translation unit compiled with -DTCL_DIR.
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*/
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#ifndef _MAGIC_TCLDIR_H
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#define _MAGIC_TCLDIR_H
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#include <stdlib.h>
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#include <stdio.h>
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#include <assert.h>
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#include <limits.h>
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/* Platform path-length limit. <limits.h> declares PATH_MAX when the system has
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* a fixed limit (4096 on Linux); provide a safe fallback when it does not. */
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#ifndef PATH_MAX
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#define PATH_MAX 4096
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#endif
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/*
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* Write magic's Tcl-runtime directory into buf (of the given size), with the
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* optional suffix appended as a path component -- the '/' directory separator is
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* supplied automatically, so pass "magic.tcl", not "/magic.tcl" (a NULL or empty
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* suffix appends nothing). A caller that wants "<dir>/magic.tcl" thus gets it in
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* one call instead of a second snprintf. Return the number of characters written
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* -- snprintf semantics, as a size_t -- or 0 on a (very unlikely) snprintf
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* encoding error. The assert catches truncation: snprintf returns the length it
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* *would* have written, so a return of >= size means the path did not fit.
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* Callers should likewise assert the returned length < their buffer size.
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*/
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static inline size_t
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MagicTclDir(char *buf, size_t size, const char *suffix)
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{
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const char *cad = getenv("CAD_ROOT");
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const char *sep;
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int n;
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if (suffix == NULL) suffix = "";
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sep = (*suffix != '\0') ? "/" : ""; /* imply the '/' separator */
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if (cad != NULL && *cad != '\0')
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n = snprintf(buf, size, "%s/magic/tcl%s%s", cad, sep, suffix);
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else
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n = snprintf(buf, size, "%s%s%s", TCL_DIR, sep, suffix);
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if (n < 0) n = 0; /* coerce encoding error to 0, assert below */
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assert((size_t)n < size);
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return (size_t)n;
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}
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#endif /* _MAGIC_TCLDIR_H */
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