From 58c5bda77b29539a805aaa503c7dad9cd5f2ddf6 Mon Sep 17 00:00:00 2001 From: Mark H Weaver Date: Sat, 6 Apr 2013 01:42:45 -0400 Subject: [PATCH] Implement efficient 'scm_unget_bytes' and use it. * libguile/ports.c (scm_i_unget_bytes): New static function. (scm_unget_bytes): New API function. (scm_unget_byte): Rewrite to simply call 'scm_i_unget_bytes'. (scm_ungetc, scm_peek_char, looking_at_bytes): Use 'scm_i_unget_bytes'. * libguile/ports.h: Add prototype for 'scm_unget_bytes'. * libguile/fports.c (scm_setvbuf): Use 'scm_unget_bytes'. --- libguile/fports.c | 3 +- libguile/ports.c | 130 ++++++++++++++++++++++++++++++++--------------------- libguile/ports.h | 1 + 3 files changed, 80 insertions(+), 54 deletions(-) diff --git a/libguile/fports.c b/libguile/fports.c index f6c3c92..ffe4334 100644 --- a/libguile/fports.c +++ b/libguile/fports.c @@ -225,8 +225,7 @@ SCM_DEFINE (scm_setvbuf, "setvbuf", 2, 1, 0, if (ndrained > 0) /* Put DRAINED back to PORT. */ - while (ndrained-- > 0) - scm_unget_byte (drained[ndrained], port); + scm_unget_bytes ((unsigned char *) drained, ndrained, port); return SCM_UNSPECIFIED; } diff --git a/libguile/ports.c b/libguile/ports.c index 47dc165..9068c5c 100644 --- a/libguile/ports.c +++ b/libguile/ports.c @@ -1789,52 +1789,25 @@ scm_end_input (SCM port) -void -scm_unget_byte (int c, SCM port) -#define FUNC_NAME "scm_unget_byte" +static void +scm_i_unget_bytes (const unsigned char *buf, size_t len, SCM port) +#define FUNC_NAME "scm_unget_bytes" { scm_t_port *pt = SCM_PTAB_ENTRY (port); + size_t old_len, new_len; scm_i_clear_pending_eof (port); - if (pt->read_buf == pt->putback_buf) - /* already using the put-back buffer. */ - { - /* enlarge putback_buf if necessary. */ - if (pt->read_end == pt->read_buf + pt->read_buf_size - && pt->read_buf == pt->read_pos) - { - size_t new_size = pt->read_buf_size * 2; - unsigned char *tmp = (unsigned char *) - scm_gc_realloc (pt->putback_buf, pt->read_buf_size, new_size, - "putback buffer"); - - pt->read_pos = pt->read_buf = pt->putback_buf = tmp; - pt->read_end = pt->read_buf + pt->read_buf_size; - pt->read_buf_size = pt->putback_buf_size = new_size; - } - /* shift any existing bytes to buffer + 1. */ - if (pt->read_pos == pt->read_end) - pt->read_end = pt->read_buf + 1; - else if (pt->read_pos != pt->read_buf + 1) - { - int count = pt->read_end - pt->read_pos; - - memmove (pt->read_buf + 1, pt->read_pos, count); - pt->read_end = pt->read_buf + 1 + count; - } - - pt->read_pos = pt->read_buf; - } - else + if (pt->read_buf != pt->putback_buf) /* switch to the put-back buffer. */ { if (pt->putback_buf == NULL) { + pt->putback_buf_size = (len > SCM_INITIAL_PUTBACK_BUF_SIZE + ? len : SCM_INITIAL_PUTBACK_BUF_SIZE); pt->putback_buf = (unsigned char *) scm_gc_malloc_pointerless - (SCM_INITIAL_PUTBACK_BUF_SIZE, "putback buffer"); - pt->putback_buf_size = SCM_INITIAL_PUTBACK_BUF_SIZE; + (pt->putback_buf_size, "putback buffer"); } pt->saved_read_buf = pt->read_buf; @@ -1842,12 +1815,59 @@ scm_unget_byte (int c, SCM port) pt->saved_read_end = pt->read_end; pt->saved_read_buf_size = pt->read_buf_size; - pt->read_pos = pt->read_buf = pt->putback_buf; - pt->read_end = pt->read_buf + 1; + /* Put read_pos at the end of the buffer, so that ungets will not + have to shift the buffer contents each time. */ + pt->read_buf = pt->putback_buf; + pt->read_pos = pt->read_end = pt->putback_buf + pt->putback_buf_size; pt->read_buf_size = pt->putback_buf_size; } - *pt->read_buf = c; + old_len = pt->read_end - pt->read_pos; + new_len = old_len + len; + + if (new_len > pt->read_buf_size) + /* The putback buffer needs to be enlarged. */ + { + size_t new_buf_size; + unsigned char *new_buf, *new_end, *new_pos; + + new_buf_size = pt->read_buf_size * 2; + if (new_buf_size < new_len) + new_buf_size = new_len; + + new_buf = (unsigned char *) + scm_gc_malloc_pointerless (new_buf_size, "putback buffer"); + + /* Put the bytes at the end of the buffer, so that future + ungets won't need to shift the buffer. */ + new_end = new_buf + new_buf_size; + new_pos = new_end - old_len; + memcpy (new_pos, pt->read_pos, old_len); + + pt->read_buf = pt->putback_buf = new_buf; + pt->read_pos = new_pos; + pt->read_end = new_end; + pt->read_buf_size = pt->putback_buf_size = new_buf_size; + } + else if (pt->read_buf + len < pt->read_pos) + /* If needed, shift the existing buffer contents up. + This should not happen unless some external code + manipulates the putback buffer pointers. */ + { + unsigned char *new_end = pt->read_buf + pt->read_buf_size; + unsigned char *new_pos = new_end - old_len; + + memmove (new_pos, pt->read_pos, old_len); + pt->read_pos = new_pos; + pt->read_end = new_end; + } + + /* Move read_pos back and copy the bytes there. */ + pt->read_pos -= len; + memcpy (pt->read_buf + (pt->read_pos - pt->read_buf), buf, len); + + if (pt->rw_active == SCM_PORT_WRITE) + scm_flush (port); if (pt->rw_random) pt->rw_active = SCM_PORT_READ; @@ -1855,6 +1875,21 @@ scm_unget_byte (int c, SCM port) #undef FUNC_NAME void +scm_unget_bytes (const unsigned char *buf, size_t len, SCM port) +{ + scm_i_unget_bytes (buf, len, port); +} + +void +scm_unget_byte (int c, SCM port) +{ + unsigned char byte; + + byte = c; + scm_i_unget_bytes (&byte, 1, port); +} + +void scm_ungetc (scm_t_wchar c, SCM port) #define FUNC_NAME "scm_ungetc" { @@ -1863,7 +1898,6 @@ scm_ungetc (scm_t_wchar c, SCM port) char result_buf[10]; const char *encoding; size_t len; - int i; if (pt->encoding != NULL) encoding = pt->encoding; @@ -1881,8 +1915,7 @@ scm_ungetc (scm_t_wchar c, SCM port) "conversion to port encoding failed", SCM_BOOL_F, SCM_MAKE_CHAR (c)); - for (i = len - 1; i >= 0; i--) - scm_unget_byte (result[i], port); + scm_i_unget_bytes ((unsigned char *) result, len, port); if (SCM_UNLIKELY (result != result_buf)) free (result); @@ -1941,7 +1974,7 @@ SCM_DEFINE (scm_peek_char, "peek-char", 0, 1, 0, SCM result; scm_t_wchar c; char bytes[SCM_MBCHAR_BUF_SIZE]; - long column, line, i; + long column, line; size_t len; if (SCM_UNBNDP (port)) @@ -1953,8 +1986,7 @@ SCM_DEFINE (scm_peek_char, "peek-char", 0, 1, 0, err = get_codepoint (port, &c, bytes, &len); - for (i = len - 1; i >= 0; i--) - scm_unget_byte (bytes[i], port); + scm_i_unget_bytes ((unsigned char *) bytes, len, port); SCM_COL (port) = column; SCM_LINUM (port) = line; @@ -2336,7 +2368,6 @@ static int looking_at_bytes (SCM port, const unsigned char *bytes, int len) { scm_t_port *pt = SCM_PTAB_ENTRY (port); - int result; int i = 0; while (i < len && scm_peek_byte_or_eof (port) == bytes[i]) @@ -2344,13 +2375,8 @@ looking_at_bytes (SCM port, const unsigned char *bytes, int len) pt->read_pos++; i++; } - - result = (i == len); - - while (i > 0) - scm_unget_byte (bytes[--i], port); - - return result; + scm_i_unget_bytes (bytes, i, port); + return (i == len); } static const unsigned char scm_utf8_bom[3] = {0xEF, 0xBB, 0xBF}; diff --git a/libguile/ports.h b/libguile/ports.h index ca5bf2f..39317f8 100644 --- a/libguile/ports.h +++ b/libguile/ports.h @@ -302,6 +302,7 @@ SCM_INTERNAL void scm_lfwrite_substr (SCM str, size_t start, size_t end, SCM_API void scm_flush (SCM port); SCM_API void scm_end_input (SCM port); SCM_API int scm_fill_input (SCM port); +SCM_API void scm_unget_bytes (const unsigned char *buf, size_t len, SCM port); SCM_API void scm_unget_byte (int c, SCM port); SCM_API void scm_ungetc (scm_t_wchar c, SCM port); SCM_API void scm_ungets (const char *s, int n, SCM port); -- 1.7.10.4