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* Copyright (c) 1993-1994 by Xerox Corporation. All rights reserved.
* 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 (
/* Boehm, October 5, 1995 4:20 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 of 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. */
/* 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. */
/* The string y is shared with the resulting CORD. Hence it should */
/* not be altered by the caller. */
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 "private/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 cordxtra.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);
/* Turn a C string into a CORD. The C string is copied, and so may */
/* subsequently be modified. */
CORD CORD_from_char_star(const char *s);
/* 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 */