# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1615674151 -3600
# Node ID a03e69c0ff65264ef6f36e00c206846aaa9290aa
# Parent  54dcc50bf1930ff7717ad60d619feb9ac34b09a9
Renamed file_open to file_context_open, providing file_open as a convenience
function that creates a context, sets the filename, opens the file, and closes
the context. Changed the string-setting function to be more immediately useful,
if more complicated in operation, for this application.

diff -r 54dcc50bf193 -r a03e69c0ff65 dstest_host_client.cc
--- a/dstest_host_client.cc	Sat Mar 13 22:38:33 2021 +0100
+++ b/dstest_host_client.cc	Sat Mar 13 23:22:31 2021 +0100
@@ -54,25 +54,11 @@
   /* Obtain access to the filesystem. */
 
   l4_cap_idx_t server = l4re_env_get_cap("server");
-  file_t context;
-
-  long err = file_context(&context, server);
-
-  if (err)
-  {
-    printf("Could not obtain context: %s\n", l4sys_errtostr(err));
-    return 1;
-  }
-
-  /* Write the filename. */
-
-  file_string_set(&context, filename, 0);
 
   /* Invoke the open method to receive the file reference. */
 
   file_t file;
-
-  err = file_open(&file, &context);
+  long err = file_open(&file, filename, server);
 
   if (err)
   {
diff -r 54dcc50bf193 -r a03e69c0ff65 dstest_test_client.cc
--- a/dstest_test_client.cc	Sat Mar 13 22:38:33 2021 +0100
+++ b/dstest_test_client.cc	Sat Mar 13 23:22:31 2021 +0100
@@ -65,7 +65,7 @@
 
   file_t file;
 
-  long err = file_open(&file, context);
+  long err = file_context_open(&file, context);
 
   if (err)
   {
diff -r 54dcc50bf193 -r a03e69c0ff65 file.cc
--- a/file.cc	Sat Mar 13 22:38:33 2021 +0100
+++ b/file.cc	Sat Mar 13 23:22:31 2021 +0100
@@ -55,36 +55,62 @@
   long err;
 
   file_init(file);
+
   err = opener.context(&file->ref);
-
   if (err)
     return err;
 
   client_Dataspace context_ds(file->ref);
 
   err = context_ds.info(&size, &flags);
-
   if (err)
     return err;
 
+  file->start_pos = 0;
+  file->end_pos = size;
+
   return ipc_attach_dataspace(file->ref, size, (void **) &file->memory);
 }
 
+/* Open a file using the given structure and context. */
+
+long file_context_open(file_t *file, file_t *context)
+{
+  client_OpenerContext openercontext(context->ref);
+  file_init(file);
+  return openercontext.open(L4_FPAGE_RW, &file->size, &file->ref);
+}
+
 /* Initialise the given file structure. */
 
 void file_init(file_t *file)
 {
   file->memory = NULL;
   file->ref = L4_INVALID_CAP;
+  file->start_pos = 0;
+  file->end_pos = 0;
+  file->data_end = 0;
 }
 
-/* Open a file using the given structure and context. */
+/* Open a file using the given structure, indicating the filename and
+   filesystem server. This is a convenience function invoking file_context and
+   file_context_open. */
 
-long file_open(file_t *file, file_t *context)
+long file_open(file_t *file, const char *filename, l4_cap_idx_t server)
 {
-  client_OpenerContext openercontext(context->ref);
-  file_init(file);
-  return openercontext.open(L4_FPAGE_RW, &file->size, &file->ref);
+  file_t context;
+  long err;
+
+  err = file_context(&context, server);
+  if (err)
+    return err;
+
+  if (!file_string_set(&context, filename, 0, NULL))
+    return -L4_ENOMEM;
+
+  err = file_context_open(file, &context);
+  file_close(&context);
+  return err;
 }
 
 
@@ -132,20 +158,26 @@
     return NULL;
 }
 
-/* Copy a string to the mapped region at the given offset, returning the number
-   of copied characters excluding the zero terminator. */
+/* Copy a string to the mapped region at the given offset, returning 1 (true)
+   where all characters were copied, 0 (false) otherwise. The precise number of
+   characters copied, excluding the zero terminator is provided via the written
+   parameter if it is not specified as NULL. */
 
-offset_t file_string_set(file_t *file, const char *data, offset_t offset)
+int file_string_set(file_t *file, const char *data, offset_t offset,
+                    offset_t *written)
 {
-  offset_t i, pos, limit = file_span(file) - 1;
+  offset_t i, pos, limit = file_span(file);
 
   /* Do not attempt to copy data with an invalid offset. */
 
-  if (offset > limit)
+  if (offset >= limit)
+  {
+    if (written != NULL)
+      *written = 0;
     return 0;
+  }
 
-  /* Copy the data to the given offset, stopping before the final byte of the
-     region. */
+  /* Copy the data to the given offset, stopping at the end of the region. */
 
   for (i = 0, pos = offset; pos < limit; i++, pos++)
   {
@@ -154,13 +186,19 @@
     /* Terminator written, can return immediately. */
 
     if (!data[i])
-      return pos - offset - 1;
+    {
+      if (written != NULL)
+        *written = pos - offset;
+      return 1;
+    }
   }
 
   /* Terminate the incomplete string at the end of the region. */
 
-  file->memory[limit] = '\0';
-  return limit - offset;
+  file->memory[limit - 1] = '\0';
+  if (written != NULL)
+    *written = limit - 1 - offset;
+  return 0;
 }
 
 // vim: tabstop=2 expandtab shiftwidth=2
diff -r 54dcc50bf193 -r a03e69c0ff65 file.h
--- a/file.h	Sat Mar 13 22:38:33 2021 +0100
+++ b/file.h	Sat Mar 13 23:22:31 2021 +0100
@@ -52,12 +52,16 @@
 
 
 
-/* File lifecycle operations. */
+/* File operations. */
 
 void file_close(file_t *file);
+long file_open(file_t *file, const char *filename, l4_cap_idx_t server);
+
+/* File lifecycle operations. */
+
 long file_context(file_t *file, l4_cap_idx_t server);
+long file_context_open(file_t *file, file_t *context);
 void file_init(file_t *file);
-long file_open(file_t *file, file_t *context);
 
 /* File access region operations. */
 
@@ -68,7 +72,7 @@
 /* Convenience functions. */
 
 char *file_string_get(file_t *file, offset_t offset);
-offset_t file_string_set(file_t *file, const char *data, offset_t offset);
+int file_string_set(file_t *file, const char *data, offset_t offset, offset_t *written);
 
 EXTERN_C_END