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/* Copyright William F. Schelter, University of Texas 1987 */
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/* This file may be copied by anyone, but changes may not
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be made without permission of the author. The author hopes it will be
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useful but cannot assume any responsibility for its use or problems
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caused by its use. The program is provided as is. */
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/* The program takes two files file1 = orig and file2 = orig.V
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tutorial% merge orig orig.V > foo
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and copies orig according to the recipe in orig.V. The advantage of
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this program is that it does this according to the context of orig.
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Thus even though orig might change slightly (eg some one added an
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extra line to the copyright notice), the same change file will
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probably still be valid.
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If the first argument is - then the orig is standard input.
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If a third argument is supplied, it is the name of a file to use
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instead of standard output.
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tutorial% merge orig orig.V | merge - change2 final
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would take the result of merge of orig and orig.V and use it to merge
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with change2 to produce the file final.
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The format of a change (.V) file is very simple: There is only ONE
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type of command in a change file. REPLACE X by Y. Here X represents
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a chunk of text in the orig file, and Y the substitution which you
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wish to make for this occurrence. The Y appears explicitly in the
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change file, while the text X may be specified fully and explicitly,
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OR by giving sufficient context from the beginning and end of X. Thus
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in general it takes three things to specify a change. The beginning
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of X (Xbegin), the end of X (Xend), and all of Y. These three pieces
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of text are separated by four delimiters. The delimiters are not
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single characters, but rather sequences of four characters. This is
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done so as to avoid having to quote the delimiter (see QUOTING below).
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The delimiters are "\n@s[" "\n@s," "\n@s|" and "\n@s]".
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NOTE: The \n (Newline) Character IS PART OF THE DELIMITER in ALL CASES.
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Thus in the above case the X text is only "X" it does not have any
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newlines in it! They belong to the delimiters. For "X\n" we would see
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The general case where X is a very long chunk of text, or perhaps something
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sensitive to copyright, so that you cannot include several pages, you
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could make Xbegin be the first few lines, and Xend the last few lines.
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All intervening lines (including the Xbegin and the Xend, would be ripped
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out, and replaced by Y.
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One cycle of the merge may be thought of as:
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The merge program looks in the change (.V) file for the next \ns[,
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in order to determine the next values for Xbegin,Xend,and Y.
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Having determined these, its position in the (.V) file will have
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advanced to after the \n@s].
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The merge program then starts at its current position in the original
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file and searches for the next occurrence of Xbegin, marking its
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beginning, then for the end of Xend. The inclusive interval so
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marked, is deleted and Y is substituted. The current position in the
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original file is now at the end of the Xend text. The next Xbegin
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text must occur after that point. Only one pass is made through the
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It is an error if the start of Xend does not follow
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the end of Xbegin. Thus Xbegin and Xend may NOT overlap. A common
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case will be that Xbegin is the entire interval and Xend = ""
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In this case the merge program, if it finds \n@s| before \n@s,
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will assume you want Xend="".
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would delete the string "Hi bill" replacing it with "new body"
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Equivalently since the E interval is empty, we could have just
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Example of change file with two changes:
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@s[(defmacro lcase (item &body body)
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@s, (setq v (car rest))
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@s|(defmacro lcase (items &body body)
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Comments are allowed in change files. In fact anything not between
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matching "\ns[" and "\ns]" is a comment.
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The first change would replace the interval of the original file
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"(defmacro.... (setq v (car rest))"
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"(defmacro lcase (items &body body)
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(setq v (cadr rest))"
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If the program could not find the interval "(defmacro.... (setq v
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(car rest))" in the orignal file it would warn you.
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The intervals in the change file, must occur in the same order as in
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the original file. There is an emacs program merge.el which can
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mechanically produce a changes file from an original and an edited
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Note: For convenience we pretend that the change file starts with
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a new line, even if it does not. Thus if @s[ are the first three
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characters of the file and CHSTART1 = \n@s[, we count this as a
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CHSTART1. Since it is in the first column, it "appears" to have
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In order to have a change which involves one of the four letter
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delimiters given above, we use the convention that "\n@@" in the first
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column translates to "\n@". You need not perform this quoting of @
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unless the merger would be confused. For example \n@(defun .. would
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be ok, since this can't be mistaken for one of our delimiters.
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Nonetheless \n@@(defun or \n@@s[ would translate to have one @ sign,
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in the merge output. The reason for not doubling all @ signs, is that
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it is very easy to scan (visually) a change you are constructing, to
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see that there are no @ signs in the first column, or at least none
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which could be confused for the four letter change delimiters
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"\n@s[","\n@s," ... A poor human constructing a change (.V) file
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should not have to sort through the X or Y text adding quoting
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Note on length: Y may be any length, but Xbegin or Xend, may only be
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/****************** THE CODE ********************/
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#define CONTEXT_LIMIT 3000 /* size of the longest delimiter or replacement */
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char ssearch_for_string();
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#define NULL_OUT (FILE *)0
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#define CHSTART1 "\n@s["
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#define CHSTART2 "\n@s,"
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#define CHSTART3 "\n@s|"
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#define CHSTART4 "\n@s]"
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#define NOACCEPT (char *) 0
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#define eofch(ch) ((unsigned char)ch == (unsigned char) EOF)
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#define myerror(string,arg) {(void)fprintf(stderr,string,arg); exit(-1);}
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{FILE *orig,*changes,*out;
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char *context,*endcontext;
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char *origname,*altername,*outname;
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context=malloc(CONTEXT_LIMIT+2);
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endcontext=malloc(CONTEXT_LIMIT+2);
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origname=filenames; altername=filenames+200; outname=filenames+400;
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/* get names from stdin */
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if (tem=scanf("%s %s %s",origname,altername,outname));
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else myerror("Three args weren't supplied: scanf returned %d\n",tem);
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else{ if (!((argc==3) || (argc==4)))
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{ myerror("Usage: merge file-orig file-changes [out-file]\n %d args given",argc-1);}
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if (argc >= 4) outname=argv[3];}};
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/* now we have the names either from command or stdin, so open files */
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if(origname[0]=='-' && origname[1]==NULL)
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orig=fopen(origname,"r");
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if (!orig) {perror(origname); exit(-1);};
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changes=fopen(altername,"r");
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if (!changes) {perror(origname); exit(-1);};
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{out=fopen(outname,"w");
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if (out); else {perror(outname); exit(-1);}}
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/* check if the file starts with chstart1 - newline. to avoid
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people thinking that starting file with @s[ is ok. */
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{char *str = CHSTART1;
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while(*(++str)) /* skip the newline start */
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{ (ch=getc(changes));
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{ ungetc(ch,changes); goto not_found;}
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{while(search_for_string(changes,CHSTART1,NULL_OUT,FALSE) > 0)
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ssearch_for_string(changes,CHSTART2,context,CONTEXT_LIMIT,TRUE,
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{myerror("\nNo end for start change context in change file:\n`%s'\n",context);};
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if (found==ACCEPT[1])
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if /* there is probably a non null endcontext */
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(ssearch_for_string(changes,CHSTART3,endcontext,
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CONTEXT_LIMIT,TRUE,NOACCEPT));
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{myerror("No %s at beginning of line to denote end of change context",
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/* skip in orig down to the end of the context,copying thru begin context */
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if (search_for_string(orig,context,out,FALSE)>0);
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else{myerror("\nCould not find the change start in original:\n`%s'\n"
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if /* copy out the changed version */
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(search_for_string(changes,CHSTART4,out,TRUE)>0);
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{myerror("No %s at beginning of line to denote end of change context",
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/*finish skipping over the region to be deleted in orig */
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{if( search_for_string(orig,endcontext,NULL_OUT,FALSE) > 0);
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{myerror("\nCould not find the end of the change in original:\n`%s'\n",
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string_match(sta,stb)
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{if (*(sta++) != *(stb++)) return 0;}
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if (*stb==0) return 1; else return 0;
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if (eofch(ch) && feof(file)) break;
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/* advance file to end of first occurrence of string, copying to out
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until the beginning of string */
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#define USE_UNQUOTE 1
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search_for_string(file,string,out,unquoting)
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result=search_for_string1(file,string,out,USE_UNQUOTE && unquoting);
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char *nxt,*lim,*ungetlim,*bp;
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char buffer[CONTEXT_LIMIT];
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{char x=((bp==buffer)? getc(file) : *--bp);
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#define mygetc(file) ((bp==buffer)? getc(file) : *--bp)
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#define myungetc(ch) *bp++ = ch
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search_for_string1(file,string,out,unquoting)
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{ /* char *nxt,*lim; */
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if (*string==NUL) return 1; unquoting;
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if ((eofch(ch)) &&(feof(file))) return 0;
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{ /* loop for checking */
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if (eofch(ch) && feof(file))
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{char *cp=string;while (cp++<=s)
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{putc(*cp,file) ; return 0;}};
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{ if (out) putc(*string,out);
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if (!(unquoting && ch==string[1] && (s-string ==2)))
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while (--cp > string)
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/* printf("<found one>"); */
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else if (out) putc(ch,out);};
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#define PUTC(ch,out) {if(ind++ < outlim) ((*(out++))=(ch));\
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ssearch_for_string1(file,string,out,outlim,unquoting,accept)
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int outlim,unquoting;
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char *string,*accept;
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if (*string==NUL) return 'a';
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if (feof(file)) return (char) 0;
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{if ((*s==(ch=getc(file)))
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|| (accept && *s==*accept && ch == *(accept+1)));
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{char *cp; cp=string;
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if (unquoting && ch==string[1] && (s-string ==2)) s--;
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{PUTC(*cp,out);cp++;}
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{PUTC(((char) 0),out);
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else if (out) PUTC(ch,out);
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ssearch_for_string(file,string,out1,outlim,unquoting,accept)
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char *string,*accept;
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result=ssearch_for_string1(file,string,out1,outlim,unquoting,accept);
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* 1)The buffering for mygetc could be more efficient (in local variable).
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* 2)Eliminate the double function calls used during debugging.
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* 3)Improve error message, for help in finding context if a change
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removed
merge.c
