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	lex.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	---
	lex.c (2505B)
	---
	1 #include "mk.h"
	2
	3 static int bquote(Biobuf, Bufblock);
	4
	5 /*
	6 * Assemble a line skipping blank lines, comments, and eliding
	7 * escaped newlines
	8 */
	9 int
	10 assline(Biobuf bp, Bufblock buf)
	11 {
	12 int c;
	13 int lastc;
	14
	15 buf->current=buf->start;
	16 while ((c = nextrune(bp, 1)) >= 0){
	17 switch(c)
	18 {
	19 case '\r': /* consumes CRs for Win95 */
	20 continue;
	21 case '\n':
	22 if (buf->current != buf->start) {
	23 insert(buf, 0);
	24 return 1;
	25 }
	26 break; /* skip empty lines */
	27 case '\\':
	28 case '\'':
	29 case '"':
	30 rinsert(buf, c);
	31 if (shellt->escapetoken(bp, buf, 1, c) == 0)
	32 Exit();
	33 break;
	34 case '`':
	35 if (bquote(bp, buf) == 0)
	36 Exit();
	37 break;
	38 case '#':
	39 lastc = '#';
	40 while ((c = Bgetc(bp)) != '\n') {
	41 if (c < 0)
	42 goto eof;
	43 if(c != '\r')
	44 lastc = c;
	45 }
	46 mkinline++;
	47 if (lastc == '\\')
	48 break; /* propagate escap…
	49 if (buf->current != buf->start) {
	50 insert(buf, 0);
	51 return 1;
	52 }
	53 break;
	54 default:
	55 rinsert(buf, c);
	56 break;
	57 }
	58 }
	59 eof:
	60 insert(buf, 0);
	61 return *buf->start != 0;
	62 }
	63
	64 /*
	65 * assemble a back-quoted shell command into a buffer
	66 */
	67 static int
	68 bquote(Biobuf bp, Bufblock buf)
	69 {
	70 int c, line, term;
	71 int start;
	72
	73 line = mkinline;
	74 while((c = Bgetrune(bp)) == ' ' \|\| c == '\t')
	75 ;
	76 if(c == '{'){
	77 term = '}'; /* rc style */
	78 while((c = Bgetrune(bp)) == ' ' \|\| c == '\t')
	79 ;
	80 } else
	81 term = '`'; /* sh style */
	82
	83 start = buf->current-buf->start;
	84 for(;c > 0; c = nextrune(bp, 0)){
	85 if(c == term){
	86 insert(buf, '\n');
	87 insert(buf,0);
	88 buf->current = buf->start+start;
	89 execinit();
	90 execsh(0, buf->current, buf, envy, shellt, shell…
	91 return 1;
	92 }
	93 if(c == '\n')
	94 break;
	95 if(c == '\'' \|\| c == '"' \|\| c == '\\'){
	96 insert(buf, c);
	97 if(!shellt->escapetoken(bp, buf, 1, c))
	98 return 0;
	99 continue;
	100 }
	101 rinsert(buf, c);
	102 }
	103 SYNERR(line);
	104 fprint(2, "missing closing %c after `\n", term);
	105 return 0;
	106 }
	107
	108 /*
	109 * get next character stripping escaped newlines
	110 * the flag specifies whether escaped newlines are to be elided or
	111 * replaced with a blank.
	112 */
	113 int
	114 nextrune(Biobuf *bp, int elide)
	115 {
	116 int c, c2;
	117 static int savec;
	118
	119 if(savec){
	120 c = savec;
	121 savec = 0;
	122 return c;
	123 }
	124
	125 for (;;) {
	126 c = Bgetrune(bp);
	127 if (c == '\\') {
	128 c2 = Bgetrune(bp);
	129 if(c2 == '\r'){
	130 savec = c2;
	131 c2 = Bgetrune(bp);
	132 }
	133 if (c2 == '\n') {
	134 savec = 0;
	135 mkinline++;
	136 if (elide)
	137 continue;
	138 return ' ';
	139 }
	140 Bungetrune(bp);
	141 }
	142 if (c == '\n')
	143 mkinline++;
	144 return c;
	145 }
	146 }