%read in chunks for lseek()able files.

configure.ac

@@ -77,8 +77,8 @@ dnl Checks for library functions.
 AC_TYPE_GETGROUPS
 AC_FUNC_MMAP
 
-AC_CHECK_FUNCS(strerror strtol lstat setrlimit sigrelse sighold sigaction \
-sysconf sigsetjmp getrusage gettimeofday mmap mprotect)
+AC_CHECK_FUNCS(strerror strtol lseek lstat setrlimit sigrelse sighold \
+sigaction sysconf sigsetjmp getrusage gettimeofday mmap mprotect)
 
 AC_CACHE_CHECK(whether getenv can be redefined, es_cv_local_getenv,
 [if test "$ac_cv_header_stdlib_h" = no || test "$ac_cv_header_stdc" = no; then

prim-io.c

@@ -413,7 +413,7 @@ PRIM(newfd) {
 	return mklist(mkstr(str("%d", newfd())), NULL);
 }
 
-/* read1 -- read one byte */
+/* read1 -- read one byte, return the byte */
 static int read1(int fd) {
 	int nread;
 	unsigned char buf;
@@ -426,6 +426,18 @@ static int read1(int fd) {
 	return nread == 0 ? EOF : buf;
 }
 
+/* readn -- read up to n bytes, return the number read */
+static int readn(int fd, char *s, size_t n) {
+	int nread;
+	do {
+		nread = read(fd, s, n);
+		SIGCHK();
+	} while (nread == -1 && errno == EINTR);
+	if (nread == -1)
+		fail("$&read", "%s", esstrerror(errno));
+	return nread;
+}
+
 PRIM(read) {
 	int c;
 	int fd = fdmap(0);
@@ -435,11 +447,36 @@ PRIM(read) {
 		freebuffer(buffer);
 	buffer = openbuffer(0);
 
-	while ((c = read1(fd)) != EOF && c != '\n')
-		if (c == '\0')
-			fail("$&read", "%%read: null character encountered");
-		else
-			buffer = bufputc(buffer, c);
+#if HAVE_LSEEK
+	if (lseek(fd, 0, SEEK_CUR) < 0) {
+#endif
+		while ((c = read1(fd)) != EOF && c != '\n')
+			if (c == '\0')
+				fail("$&read", "%%read: null character encountered");
+			else
+				buffer = bufputc(buffer, c);
+#if HAVE_LSEEK
+	} else {
+		int n;
+		char *np, *zp;
+		char s[BUFSIZE];
+		c = EOF;
+		while ((n = readn(fd, s, BUFSIZE)) > 0) {
+			c = 0;
+			if ((np = strchr(s, '\n')) != NULL) {
+				lseek(fd, 1 + ((np - s) - n), SEEK_CUR);
+				n = np - s;
+			}
+			if ((zp = memchr(s, '\0', n)) != NULL) {
+				lseek(fd, 1 + ((zp - s) - n), SEEK_CUR);
+				fail("$&read", "%%read: null character encountered");
+			}
+			buffer = bufncat(buffer, s, n);
+			if (np != NULL && *np == '\n')
+				break;
+		}
+	}
+#endif
 
 	if (c == EOF && buffer->current == 0) {
 		freebuffer(buffer);

test/tests/read.es

@@ -0,0 +1,38 @@
+#!/usr/local/bin/es
+
+test 'null reading' {
+	let (tmp = `{mktemp test-nul.XXXXXX})
+	unwind-protect {
+		echo first line	 > $tmp
+		./testrun 0	>> $tmp
+
+		let (fl = (); ex = (); remainder = ()) {
+			catch @ e {
+				ex = $e
+				remainder = <=%read
+			} {
+				fl = <=%read
+				%read
+			} < $tmp
+			assert {~ $fl 'first line'} 'seeking read reads valid line'
+			assert {~ $ex(3) *'null character encountered'*} 'seeking read throws exception correctly'
+			assert {~ $remainder 'sult 6'} 'seeking read leaves file in correct state:' $remainder
+		}
+
+		let ((fl ex remainder) = `` \n {
+			let (fl = ())
+			cat $tmp | catch @ e {
+				echo $fl\n$e(3)\n^<=%read
+			} {
+				fl = <=%read
+				%read
+			}
+		}) {
+			assert {~ $fl 'first line'} 'non-seeking read reads valid line'
+			assert {~ $ex *'null character encountered'*} 'non-seeking read throws exception correctly'
+			assert {~ $remainder 'sult 6'} 'non-seeking read leaves file in correct state'
+		}
+	} {
+		rm -f $tmp
+	}
+}