OS/2 Shareware BBS: 10 Tools/10-Tools.zip/sa104os2.zip/SATHR104.ZIP/SATHER/SYSTEM/GC/CORD/CORD.H

C/C++ Source or Header | 1995-01-09 | 14KB | 322 lines

/*
 * Copyright (c) 1993-1994 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 *
 * Author: Hans-J. Boehm ([e-mail])
 */
/* Boehm, October 4, 1994 5:34 pm PDT */

/*
 * Cords are immutable character strings.  A number of operations
 * on long cords are much more efficient than their strings.h counterpart.
 * In particular, concatenation takes constant time independent of the length
 * of the arguments.  (Cords are represented as trees, with internal
 * nodes representing concatenation and leaves consisting of either C
 * strings or a functional description of the string.)
 *
 * The following are reasonable applications of cords.  They would perform
 * unacceptably if C strings were used:
 * - A compiler that produces assembly language output by repeatedly
 *   concatenating instructions onto a cord representing the output file.
 * - A text editor that converts the input file to a cord, and then
 *   performs editing operations by producing a new cord representing
 *   the file after echa character change (and keeping the old ones in an
 *   edit history)
 *
 * For optimal performance, cords should be built by
 * concatenating short sections.
 * This interface is designed for maximum compatibility with C strings.
 * ASCII NUL characters may be embedded in cords using CORD_from_fn.
 * This is handled correctly, but CORD_to_char_star will produce a string
 * with embedded NULs when given such a cord.
 *
 * This interface is fairly big, largely for performance reasons.
 * The most basic constants and functions:
 *
 * CORD - the type fo a cord;
 * CORD_EMPTY - empty cord;
 * CORD_len(cord) - length of a cord;
 * CORD_cat(cord1,cord2) - concatenation of two cords;
 * CORD_substr(cord, start, len) - substring (or subcord);
 * CORD_pos i;  CORD_FOR(i, cord) {  ... CORD_pos_fetch(i) ... } -
 *    examine each character in a cord.  CORD_pos_fetch(i) is the char.
 * CORD_fetch(int i) - Retrieve i'th character (slowly).
 * CORD_cmp(cord1, cord2) - compare two cords.
 * CORD_from_file(FILE * f) - turn a read-only file into a cord.
 * CORD_to_char_star(cord) - convert to C string.
 *   (Non-NULL C constant strings are cords.)
 * CORD_printf (etc.) - cord version of printf. Use %r for cords.
 */
# ifndef CORD_H

# define CORD_H
# include <stddef.h>
# include <stdio.h>
/* Cords have type const char *.  This is cheating quite a bit, and not    */
/* 100% portable.  But it means that nonempty character string        */
/* constants may be used as cords directly, provided the string is    */
/* never modified in place.  The empty cord is represented by, and    */
/* can be written as, 0.                        */

typedef const char * CORD;

/* An empty cord is always represented as nil     */
# define CORD_EMPTY 0

/* Is a nonempty cord represented as a C string? */
#define CORD_IS_STRING(s) (*(s) != '\0')

/* Concatenate two cords.  If the arguments are C strings, they may     */
/* not be subsequently altered.                        */
CORD CORD_cat(CORD x, CORD y);

/* Concatenate a cord and a C string with known length.  Except for the    */
/* empty string case, this is a special case of CORD_cat.  Since the    */
/* length is known, it can be faster.                    */
CORD CORD_cat_char_star(CORD x, const char * y, size_t leny);

/* Compute the length of a cord */
size_t CORD_len(CORD x);

/* Cords may be represented by functions defining the ith character */
typedef char (* CORD_fn)(size_t i, void * client_data);

/* Turn a functional description into a cord.     */
CORD CORD_from_fn(CORD_fn fn, void * client_data, size_t len);

/* Return the substring (subcord really) of x with length at most n,    */
/* starting at position i.  (The initial character has position 0.)    */
CORD CORD_substr(CORD x, size_t i, size_t n);

/* Return the argument, but rebalanced to allow more efficient       */
/* character retrieval, substring operations, and comparisons.        */
/* This is useful only for cords that were built using repeated     */
/* concatenation.  Guarantees log time access to the result, unless    */
/* x was obtained through a large number of repeated substring ops    */
/* or the embedded functional descriptions take longer to evaluate.    */
/* May reallocate significant parts of the cord.  The argument is not    */
/* modified; only the result is balanced.                */
CORD CORD_balance(CORD x);

/* The following traverse a cord by applying a function to each     */
/* character.  This is occasionally appropriate, especially where    */
/* speed is crucial.  But, since C doesn't have nested functions,    */
/* clients of this sort of traversal are clumsy to write.  Consider    */
/* the functions that operate on cord positions instead.        */

/* Function to iteratively apply to individual characters in cord.    */
typedef int (* CORD_iter_fn)(char c, void * client_data);

/* Function to apply to substrings of a cord.  Each substring is a     */
/* a C character string, not a general cord.                */
typedef int (* CORD_batched_iter_fn)(const char * s, void * client_data);
# define CORD_NO_FN ((CORD_batched_iter_fn)0)

/* Apply f1 to each character in the cord, in ascending order,        */
/* starting at position i. If                        */
/* f2 is not CORD_NO_FN, then multiple calls to f1 may be replaced by    */
/* a single call to f2.  The parameter f2 is provided only to allow    */
/* some optimization by the client.  This terminates when the right    */
/* end of this string is reached, or when f1 or f2 return != 0.  In the    */
/* latter case CORD_iter returns != 0.  Otherwise it returns 0.        */
/* The specified value of i must be < CORD_len(x).            */
int CORD_iter5(CORD x, size_t i, CORD_iter_fn f1,
           CORD_batched_iter_fn f2, void * client_data);

/* A simpler version that starts at 0, and without f2:    */
int CORD_iter(CORD x, CORD_iter_fn f1, void * client_data);
# define CORD_iter(x, f1, cd) CORD_iter5(x, 0, f1, CORD_NO_FN, cd)

/* Similar to CORD_iter5, but end-to-beginning.    No provisions for    */
/* CORD_batched_iter_fn.                        */
int CORD_riter4(CORD x, size_t i, CORD_iter_fn f1, void * client_data);

/* A simpler version that starts at the end:    */
int CORD_riter(CORD x, CORD_iter_fn f1, void * client_data);

/* Functions that operate on cord positions.  The easy way to traverse    */
/* cords.  A cord position is logically a pair consisting of a cord    */
/* and an index into that cord.  But it is much faster to retrieve a    */
/* charcter based on a position than on an index.  Unfortunately,    */
/* positions are big (order of a few 100 bytes), so allocate them with    */
/* caution.                                */
/* Things in cord_pos.h should be treated as opaque, except as        */
/* described below.  Also note that                    */
/* CORD_pos_fetch, CORD_next and CORD_prev have both macro and function    */
/* definitions.  The former may evaluate their argument more than once. */
# include "cord_pos.h"

/*
    Visible definitions from above:

    typedef <OPAQUE but fairly big> CORD_pos[1];

    /* Extract the cord from a position:
    CORD CORD_pos_to_cord(CORD_pos p);

    /* Extract the current index from a position:
    size_t CORD_pos_to_index(CORD_pos p);

    /* Fetch the character located at the given position:
    char CORD_pos_fetch(CORD_pos p);

    /* Initialize the position to refer to the given cord and index.
    /* Note that this is the most expensive function on positions:
    void CORD_set_pos(CORD_pos p, CORD x, size_t i);

    /* Advance the position to the next character.
    /* P must be initialized and valid.
    /* Invalidates p if past end:
    void CORD_next(CORD_pos p);

    /* Move the position to the preceding character.
    /* P must be initialized and valid.
    /* Invalidates p if past beginning:
    void CORD_prev(CORD_pos p);

    /* Is the position valid, i.e. inside the cord?
    int CORD_pos_valid(CORD_pos p);
*/
# define CORD_FOR(pos, cord) \
    for (CORD_set_pos(pos, cord, 0); CORD_pos_valid(pos); CORD_next(pos))


/* An out of memory handler to call.  May be supplied by client.    */
/* Must not return.                            */
extern void (* CORD_oom_fn)(void);

/* Dump the representation of x to stdout in an implementation defined    */
/* manner.  Intended for debugging only.                */
void CORD_dump(CORD x);

/* The following could easily be implemented by the client.  They are    */
/* provided in cord_xtra.c for convenience.                */

/* Concatenate a character to the end of a cord.    */
CORD CORD_cat_char(CORD x, char c);

/* Concatenate n cords.    */
CORD CORD_catn(int n, /* CORD */ ...);

/* Return the character in CORD_substr(x, i, 1)      */
char CORD_fetch(CORD x, size_t i);

/* Return < 0, 0, or > 0, depending on whether x < y, x = y, x > y    */
int CORD_cmp(CORD x, CORD y);

/* A generalization that takes both starting positions for the         */
/* comparison, and a limit on the number of characters to be compared.    */
int CORD_ncmp(CORD x, size_t x_start, CORD y, size_t y_start, size_t len);

/* Find the first occurrence of s in x at position start or later.    */
/* Return the position of the first character of s in x, or        */
/* CORD_NOT_FOUND if there is none.                    */
size_t CORD_str(CORD x, size_t start, CORD s);

/* Return a cord consisting of i copies of (possibly NUL) c.  Dangerous    */
/* in conjunction with CORD_to_char_star.                */
/* The resulting representation takes constant space, independent of i.    */
CORD CORD_chars(char c, size_t i);
# define CORD_nul(i) CORD_chars('\0', (i))

/* Turn a file into cord.  The file must be seekable.  Its contents    */
/* must remain constant.  The file may be accessed as an immediate    */
/* result of this call and/or as a result of subsequent accesses to     */
/* the cord.  Short files are likely to be immediately read, but    */
/* long files are likely to be read on demand, possibly relying on     */
/* stdio for buffering.                            */
/* We must have exclusive access to the descriptor f, i.e. we may    */
/* read it at any time, and expect the file pointer to be        */
/* where we left it.  Normally this should be invoked as        */
/* CORD_from_file(fopen(...))                        */
/* CORD_from_file arranges to close the file descriptor when it is no    */
/* longer needed (e.g. when the result becomes inaccessible).        */
/* The file f must be such that ftell reflects the actual character    */
/* position in the file, i.e. the number of characters that can be     */
/* or were read with fread.  On UNIX systems this is always true.  On    */
/* MS Windows systems, f must be opened in binary mode.            */
CORD CORD_from_file(FILE * f);

/* Equivalent to the above, except that the entire file will be read    */
/* and the file pointer will be closed immediately.            */
/* The binary mode restriction from above does not apply.        */
CORD CORD_from_file_eager(FILE * f);

/* Equivalent to the above, except that the file will be read on demand.*/
/* The binary mode restriction applies.                    */
CORD CORD_from_file_lazy(FILE * f);

/* Turn a cord into a C string.    The result shares no structure with    */
/* x, and is thus modifiable.                        */
char * CORD_to_char_star(CORD x);

/* Identical to the above, but the result may share structure with    */
/* the argument and is thus not modifiable.                */
const char * CORD_to_const_char_star(CORD x);

/* Write a cord to a file, starting at the current position.  No    */
/* trailing NULs are newlines are added.                */
/* Returns EOF if a write error occurs, 1 otherwise.            */
int CORD_put(CORD x, FILE * f);

/* "Not found" result for the following two functions.            */
# define CORD_NOT_FOUND ((size_t)(-1))

/* A vague analog of strchr.  Returns the position (an integer, not    */
/* a pointer) of the first occurrence of (char) c inside x at position     */
/* i or later. The value i must be < CORD_len(x).            */
size_t CORD_chr(CORD x, size_t i, int c);

/* A vague analog of strrchr.  Returns index of the last occurrence    */
/* of (char) c inside x at position i or earlier. The value i        */
/* must be < CORD_len(x).                        */
size_t CORD_rchr(CORD x, size_t i, int c);


/* The following are also not primitive, but are implemented in     */
/* cordprnt.c.  They provide functionality similar to the ANSI C    */
/* functions with corresponding names, but with the following        */
/* additions and changes:                        */
/* 1. A %r conversion specification specifies a CORD argument.  Field    */
/*    width, precision, etc. have the same semantics as for %s.        */
/*    (Note that %c,%C, and %S were already taken.)            */
/* 2. The format string is represented as a CORD.                */
/* 3. CORD_sprintf and CORD_vsprintf assign the result through the 1st    */     /*    argument.    Unlike their ANSI C versions, there is no need to guess    */
/*    the correct buffer size.                        */
/* 4. Most of the conversions are implement through the native         */
/*    vsprintf.  Hence they are usually no faster, and             */
/*    idiosyncracies of the native printf are preserved.  However,    */
/*    CORD arguments to CORD_sprintf and CORD_vsprintf are NOT copied;    */
/*    the result shares the original structure.  This may make them    */
/*    very efficient in some unusual applications.            */
/*    The format string is copied.                    */
/* All functions return the number of characters generated or -1 on    */
/* error.  This complies with the ANSI standard, but is inconsistent    */
/* with some older implementations of sprintf.                */

/* The implementation of these is probably less portable than the rest    */
/* of this package.                            */

#ifndef CORD_NO_IO

#include <stdarg.h>

int CORD_sprintf(CORD * out, CORD format, ...);
int CORD_vsprintf(CORD * out, CORD format, va_list args);
int CORD_fprintf(FILE * f, CORD format, ...);
int CORD_vfprintf(FILE * f, CORD format, va_list args);
int CORD_printf(CORD format, ...);
int CORD_vprintf(CORD format, va_list args);

#endif /* CORD_NO_IO */

# endif /* CORD_H */