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+/* 
+ * 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 (boehm@parc.xerox.com)
+ */
+/* 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 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.					*/
+/* 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 */