/*********************************************************************** This file provides alternative functions for several VMS VMS C library routines which either unacceptable, or incorrect, implementations. They have been developed and tested under VMS Version 4.4, but indications are that they apply to earlier versions, back to 3.2 at least. They should be retested with each new release of VMS C. Contents: EXIT FSEEK FTELL GETCHAR GETENV READ UNGETC getlogin qsort system tell unlink The VAX VMS file system record structure has unfortunate consequences for random access files. By default, text files written by most system utilities, and languages other than C, have a variable length record format, in which a 16-bit character count is aligned on an even-byte boundary in the disk block b(always 512 bytes in VMS, independent of record and file formats), followed by bytes of data. Binary files, such as .EXE, .OBJ, and TeX .DVI and font files, all use a 512-byte fixed record format which has no explicit length field. No file byte count is stored; instead, the block count, and the offset of the last data byte in the last block are recorded in the file header (do ``DUMP/HEADER filespec'' to see it). For binary files with fixed-length records, the last block is normally assumed to be full, and consequently, file transfer of binary data from other machines via Kermit, FTP, or DCL COPY from ANSI tapes, generally fails because the input file length is not a multiple of 512. This record organization may be contrasted with the STREAM, STREAM_LF, and STREAM_CR organizations supported from Version 4.0; in these, disk blocks contain a continuous byte stream in which nothing, or LF, or CR, is recognized as a record terminator. These formats are similar to the Unix and TOPS-20 file system formats which also use continuous byte streams. For C, this means that a program operating on a file in record format cannot count input characters and expect that count to be the same value as the offset parameter passed to fseek(), which numerous C programs assume to be the case. The draft ANSI C standard, and Harbison and Steele's ``C Reference Manual'', emphasize that only values returned by ftell() should be used as arguments to fseek(), allowing the program to return to a position previously read or written. UNFORTUNATELY, VMS C ftell() DOES NOT RETURN A CORRECT OFFSET VALUE FOR RECORD FILES. Instead, for record files, it returns the byte offset of the start of the current record, no matter where in that record the current position may be. This misbehavior is completely unnecessary, since the replacements below perform correctly, and are written entirely in C. Another problem is that ungetc(char c, FILE* fp) is unreliable. VMS C implements characters as signed 8-bit integers (so do many other C implementations). fgetc(FILE* fp) returns an int, not a char, whose value is EOF (-1) in the event of end-of-file; however, this value will also be returned for a character 0xFF, so it is essential to use feof(FILE *fp) to test for a true end-of-file condition when EOF is returned. ungetc() checks the sign of its argument c, and if it is negative (which it will be for 128 of the 256 signed bytes), REFUSES TO PUT IT BACK IN THE INPUT STREAM, on the assumption that c is really EOF. This too can be fixed; ungetc() should only do nothing if feof() indicates a true end-of-file condition. The overhead of this is trivial, since feof() is actually implemented as a macro which does nothing more than a logical AND and compare-with-zero. getchar() waits for a to be typed when stdin is a terminal; the replacement vms_getchar() remedies this. Undoubtedly other deficiencies in VMS C will reveal themselves. VMS read() returns only a single disk block on each call. Its replacment, vms_read(), will return the requested number of bytes, if possible. There are also a few Unix standard functions which are unimplemented. qsort() is not provided. getlogin() and unlink() have VMS equivalents provided below. tell() is considered obsolete, since its functionality is available from lseek(), but it is still seen in a few programs, so is provided below. getenv() fails if the name contains a colon; its replacement allows the colon. In the interest of minimal source perturbation, replacements for VMS functions are given the same names, but prefixed "vms_". For readability, the original names are preserved, but are converted to upper-case: #define FTELL vms_ftell #define FSEEK vms_fseek #define GETCHAR vms_getchar #define GETENV vms_getenv #define UNGETC vms_ungetc These are only defined to work correctly for fixed length 512-byte records, and no check is made that the file has that organization (it is possible, but not without expensive calls to fstat(), or access to internal library structures). [02-Apr-87] -- Nelson H.F. Beebe, University of Utah Center for Scientific Computing ***********************************************************************/ #define EXIT vms_exit #define FTELL vms_ftell #define FSEEK vms_fseek #define GETENV vms_getenv #define GETCHAR vms_getchar #define READ vms_read #define UNGETC vms_ungetc #include #include #include #include #include #include /* need for vms_getchar() */ #include #ifdef __GNUC__ #include #endif void EXIT(int code); long FTELL(FILE *fp); long FSEEK(FILE *fp, long n, long dir); long UNGETC(char c, FILE *fp); int GETCHAR(void); int READ(int file_desc, char *buffer, int nbytes); char *GETENV(char *name); char *getlogin(void); long tell(int handle); int unlink(char *filename); /**********************************************************************/ /*-->EXIT*/ void vms_exit(int code) { switch (code) { case 0: exit(1); /* success */ break; default: exit(2); /* error */ break; } } /**********************************************************************/ /*-->FSEEK*/ /* VMS fseek() and ftell() on fixed-length record files work correctly only at block boundaries. This replacement code patches in the offset within the block. Directions from current position and from end-of-file are converted to absolute positions, and then the code for that case is invoked. */ long FSEEK(FILE *fp, long n, long dir) { long k,m,pos,val,oldpos; struct stat buffer; for (;;) /* loops only once or twice */ { switch (dir) { case 0: /* from BOF */ oldpos = FTELL(fp); /* get current byte offset in file */ k = n & 511; /* offset in 512-byte block */ m = n >> 9; /* relative block number in file */ if (((*fp)->_cnt) && ((oldpos >> 9) == m)) /* still in same block */ { val = 0; /* success */ (*fp)->_ptr = ((*fp)->_base) + k; /* reset pointers to requested byte */ (*fp)->_cnt = 512 - k; } else { val = fseek(fp,m << 9,0); /* move to start of requested 512-byte block */ if (val == 0) /* success */ { (*fp)->_cnt = 0; /* indicate empty buffer */ (void)fgetc(fp); /* force refill of buffer */ (*fp)->_ptr = ((*fp)->_base) + k; /* reset pointers to requested byte */ (*fp)->_cnt = 512 - k; } } return(val); case 1: /* from current pos */ pos = FTELL(fp); if (pos == EOF) /* then error */ return (EOF); n += pos; dir = 0; break; /* go do case 0 */ case 2: /* from EOF */ val = fstat(fileno(fp),&buffer); if (val == EOF) /* then error */ return (EOF); n += buffer.st_size - 1; /* convert filesize to offset and */ /* add to requested offset */ dir = 0; break; /* go do case 0 */ default: /* illegal direction parameter */ return (EOF); } } } /**********************************************************************/ /*-->FTELL*/ /* With fixed-length record files, ftell() returns the offset of the start of block. To get the true position, this must be biased by the offset within the block. */ long FTELL(FILE *fp) { char c; long pos; long val; if ((*fp)->_cnt == 0) /* buffer empty--force refill */ { c = fgetc(fp); val = UNGETC(c,fp); if (val != c) return (EOF); /* should never happen */ } pos = ftell(fp); /* this returns multiple of 512 (start of block) */ if (pos >= 0) /* then success--patch in offset in block */ pos += ((*fp)->_ptr) - ((*fp)->_base); return (pos); } /**********************************************************************/ /*-->GETCHAR*/ static int tt_channel = -1; /* terminal channel for image QIO's */ #define FAILED(status) (~(status) & 1) /* failure if LSB is 0 */ int GETCHAR() { int ret_char; /* character returned */ int status; /* system service status */ static $DESCRIPTOR(sys_in,"TT:"); if (tt_channel == -1) /* then first call--assign channel */ { status = sys$assign(&sys_in,&tt_channel,0,0); if (FAILED(status)) lib$stop(status); } ret_char = 0; status = sys$qiow(0,tt_channel,IO$_TTYREADALL | IO$M_NOECHO,0,0,0, &ret_char,1,0,0,0,0); if (FAILED(status)) lib$stop(status); return (ret_char); } /**********************************************************************/ /*-->READ*/ int READ(register int file_desc,register char *buffer,register int nbytes) { register int ngot; register int left; for ((left = nbytes, ngot = 0); left > 0; /* NOOP */) { ngot = read(file_desc,buffer,left); if (ngot < 0) return (-1); /* error occurred */ buffer += ngot; left -= ngot; } return(nbytes-left); } /**********************************************************************/ /*-->UNGETC*/ long UNGETC(char c, FILE *fp) /* VMS ungetc() is a no-op if c < 0 */ { /* (which is half the time!) */ if ((c == EOF) && feof(fp)) return (EOF); /* do nothing at true end-of-file */ else if ((*fp)->_cnt >= 512)/* buffer full--no fgetc() done in this block!*/ return (EOF); /* must be user error if this happens */ else /* put the character back in the buffer */ { (*fp)->_cnt++; /* increase count of characters left */ (*fp)->_ptr--; /* backup pointer to next available char */ *((*fp)->_ptr) = c; /* save the character */ return (c); /* and return it */ } } /**********************************************************************/ /*-->getenv*/ char* GETENV(char *name) { char* p; char* result; char ucname[256]; p = ucname; while (*name) /* VMS logical names must be upper-case */ { *p++ = islower(*name) ? toupper(*name) : *name; ++name; } *p = '\0'; p = strchr(ucname,':'); /* colon in name? */ if (p == (char *)NULL) /* no colon in name */ result = getenv(ucname); else /* try with and without colon */ { result = getenv(ucname); if (result == (char *)NULL) { *p = '\0'; result = getenv(ucname); *p = ':'; } } return (result); } /**********************************************************************/ /*-->getlogin*/ char* getlogin() { return ((char *)getenv("USER")); /* use equivalent VMS routine */ } /**********************************************************************/ /*-->qsort*/ /*********************************************************************** TeXindex uses the standard Unix library function qsort() for record sorting. Unfortunately, qsort() is not a stable sorting algorithm, so input order is not necessarily preserved for equal sort keys. This is important, because the sorting is case-independent, while the actual entries may not be. For example, the input \entry{i}{22}{{\CODE{i}}} \entry{i}{42}{{\CODE{i}}} \entry{I}{41}{{\CODE{I}}} \entry{I}{42}{{\CODE{I}}} produces \initial {I} \entry {{\CODE{i}}}{22} \entry {{\CODE{I}}}{41--42} \entry {{\CODE{i}}}{42} instead of the correct \initial {I} \entry {{\CODE{i}}}{22, 42} \entry {{\CODE{I}}}{41--42} We therefore provide this stable shellsort replacement for qsort() based on the code given on p. 116 of Kernighan and Ritchie, ``The C Programming Language'', Prentice-Hall (1978). This has order N**1.5 average performance, which is usually slower than qsort(). In the interests of simplicity, we make no attempt to handle short sequences by alternative methods. [07-Nov-86] ***********************************************************************/ #if VMS_QSORT #define BASE(i) &base[(i)*width] void qsort(base, nel, width, compar) char base[]; /* start of data in memory */ int nel; /* number of elements to be sorted */ int width; /* size (in bytes) of each element */ int (*compar)(); /* comparison function */ { int gap; int i; int j; register int k; /* inner exchange loop parameters */ register char* p; register char* q; register char c; for (gap = nel/2; gap > 0; gap /= 2) { for (i = gap; i < nel; i++) { for (j = i-gap; j >= 0; j -= gap) { p = BASE(j); q = BASE(j+gap); if ((*compar)(p,q) <= 0) break; /* exit j loop */ else { for (k = 0; k < width; (++p, ++q, ++k)) { c = *q; *q = *p; *p = c; } } } } } } #endif /********************************************************************** *-->system* int system(char *s) { struct dsc$descriptor t; t.dsc$w_length = strlen(s); t.dsc$a_pointer = s; t.dsc$b_class = DSC$K_CLASS_S; t.dsc$b_dtype = DSC$K_DTYPE_T; return (LIB$SPAWN(&t) == SS$_NORMAL) ? 0 : 127; } **********************************************************************/ /*-->tell*/ long tell(int handle) { return (lseek(handle,0L,1)); } /**********************************************************************/ /*-->unlink*/ int unlink(char *filename) { return (delete(filename)); /* use equivalent VMS routine */ }