From 3abd3e0bccc0e1718822348081058bcb7b356885 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Tue, 17 Dec 2019 22:44:24 +0100
Subject: [PATCH] mescc: Mes C Library: lseek: Be careful clearing read buffer.

* lib/linux/lseek.c (_lseek): New function.
* lib/linux/lseek.c (lseek): Use it to check if we should reset read
buffer.
* lib/mes/__buffered_read.c (__read_buffer_max): New variable.
(__buffered_read_init): Add environment override: MES_READ_BUFFER.
(__buffered_read): Use it.
---
 lib/linux/lseek.c         | 12 +++++++++++
 lib/mes/__buffered_read.c | 42 +++++++++++++++++++++++++++++++++------
 lib/posix/open.c          |  2 +-
 lib/stdio/fopen.c         |  4 +---
 4 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/lib/linux/lseek.c b/lib/linux/lseek.c
index 94f2f9f7..f71af59f 100644
--- a/lib/linux/lseek.c
+++ b/lib/linux/lseek.c
@@ -24,9 +24,21 @@
 #include <stdio.h>
 #include <sys/types.h>
 
+#if !__MESC__ /* FIXME: We want bin/mes-mescc's x86-linux sha256sum to stay the same. */
+off_t
+_lseek (int filedes, off_t offset, int whence)
+{
+  return _sys_call3 (SYS_lseek, (int) filedes, (long) offset, (int) whence);
+}
+#endif
+
 off_t
 lseek (int filedes, off_t offset, int whence)
 {
+#if !__MESC__ /* FIXME: We want bin/mes-mescc's x86-linux sha256sum to stay the same. */
+  if (_lseek (filedes, 0, SEEK_CUR) == -1)
+    return -1;
+#endif
   size_t skip = __buffered_read_clear (filedes);
   if (whence == SEEK_CUR)
     offset -= skip;
diff --git a/lib/mes/__buffered_read.c b/lib/mes/__buffered_read.c
index e47cca53..bac1f309 100644
--- a/lib/mes/__buffered_read.c
+++ b/lib/mes/__buffered_read.c
@@ -22,7 +22,13 @@
 #include <stdlib.h>
 #include <string.h>
 
+#if !__MESC__
+#define __READ_BUFFER_MAX 128
+int __read_buffer_max;
+#else /* FIXME: We want bin/mes-mescc's x86-linux sha256sum to stay the same. */
 #define __READ_BUFFER_MAX 100
+#define __read_buffer_max 100
+#endif
 
 struct __read_buffer
 {
@@ -36,7 +42,21 @@ void
 __buffered_read_init (int filedes)
 {
   if (!__read_cache)
-    __read_cache = (struct __read_buffer *) malloc (sizeof (struct __read_buffer) * __FILEDES_MAX);
+    {
+      __read_cache = (struct __read_buffer *) malloc (sizeof (struct __read_buffer) * __FILEDES_MAX);
+#if !__MESC__
+      __read_buffer_max = __READ_BUFFER_MAX;
+      char *p = getenv ("MES_READ_BUFFER");
+      if (p)
+        {
+          __read_buffer_max = atoi (p);
+          if (__read_buffer_max < 0)
+            __read_buffer_max = 0;
+          if (__read_buffer_max > __READ_BUFFER_MAX)
+            __read_buffer_max = __READ_BUFFER_MAX;
+        }
+#endif
+    }
 }
 
 size_t
@@ -55,23 +75,33 @@ __buffered_read (int filedes, void *buffer, size_t size)
   __buffered_read_init (filedes);
   struct __read_buffer *cache = &__read_cache[filedes];
   char *p = buffer;
-  if (!cache->size && size > __READ_BUFFER_MAX)
+  if (!cache->size && size > __read_buffer_max)
     return _read (filedes, buffer, size);
   while (cache->size > 0 && todo)
     {
       todo--;
-      *p++ = cache->string[__READ_BUFFER_MAX - cache->size--];
+      *p++ = cache->string[__read_buffer_max - cache->size--];
     }
   if (todo)
     {
-      ssize_t bytes = _read (filedes, cache->string, __READ_BUFFER_MAX);
+#if !__MESC__
+      if (todo > __read_buffer_max)
+        return size - todo + _read (filedes, p, todo);
+      if (__mes_debug () > 4)
+        {
+          eputs ("__buffered_read: ");
+          eputs (itoa (__read_buffer_max));
+          eputs ("\n");
+        }
+#endif
+      ssize_t bytes = _read (filedes, cache->string, __read_buffer_max);
       if (bytes < 0)
         return -1;
       if (bytes)
         {
           cache->size = bytes;
-          if (bytes < __READ_BUFFER_MAX)
-            memmove (cache->string + __READ_BUFFER_MAX - bytes, cache->string, bytes);
+          if (bytes < __read_buffer_max)
+            memmove (cache->string + __read_buffer_max - bytes, cache->string, bytes);
           return size - todo + __buffered_read (filedes, p, todo);
         }
     }
diff --git a/lib/posix/open.c b/lib/posix/open.c
index ad76297d..490c3ec9 100644
--- a/lib/posix/open.c
+++ b/lib/posix/open.c
@@ -42,5 +42,5 @@ open (char const *file_name, int flags, ...)
       return r;
     }
   else
-    return _open2(file_name, flags);
+    return _open2 (file_name, flags);
 }
diff --git a/lib/stdio/fopen.c b/lib/stdio/fopen.c
index 6342e0a2..3164c11e 100644
--- a/lib/stdio/fopen.c
+++ b/lib/stdio/fopen.c
@@ -45,7 +45,7 @@ fopen (char const *file_name, char const *opentype)
       int flags = O_RDWR;
       if (opentype[0] == 'a')
         flags |= O_APPEND;
-      fd = open (file_name, flags, mode);
+      fd = _open3 (file_name, flags, mode);
     }
   else if (opentype[0] == 'w' || opentype[0] == 'a' || !strcmp (opentype, "r+"))
     {
@@ -72,5 +72,3 @@ fopen (char const *file_name, char const *opentype)
     fd = 0;
   return (FILE *) (long) fd;
 }
-
-#undef open