# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1616025595 -3600
# Node ID 0073e2ca6c75cf24c2093d5624deb2da4f63c67b
# Parent  108c08c35100d171114ae0260d28ebb531bb8f54
Introduced initial support for resizing files.

diff -r 108c08c35100 -r 0073e2ca6c75 dstest_block_client.cc
--- a/dstest_block_client.cc	Wed Mar 17 00:10:47 2021 +0100
+++ b/dstest_block_client.cc	Thu Mar 18 00:59:55 2021 +0100
@@ -33,6 +33,24 @@
 
 
 
+static void show(file_t *file, unsigned long step, unsigned long sample)
+{
+  /* Allocate a buffer for sampling from the file. */
+
+  char buf[sample + 1];
+
+  for (unsigned long offset = 0; offset < file_populated_span(file); offset += step)
+  {
+    unsigned long remaining = file_populated_span(file) - offset;
+    unsigned long sample_remaining = remaining < sample ? remaining : sample;
+
+    printf("%ld bytes from %p...\n", sample_remaining, (file->memory + offset));
+    strncpy(buf, (file->memory + offset), sample_remaining);
+    buf[sample_remaining] = '\0';
+    printf("%s\n", buf);
+  }
+}
+
 int main(int argc, char *argv[])
 {
   if (argc < 4)
@@ -47,10 +65,6 @@
   unsigned long step = atoi(argv[2]);
   unsigned long sample = atoi(argv[3]);
 
-  /* Allocate a buffer for sampling from the file. */
-
-  char buf[sample + 1];
-
   /* Obtain access to the filesystem. */
 
   l4_cap_idx_t server = l4re_env_get_cap("server");
@@ -76,16 +90,39 @@
     return 1;
   }
 
+  show(&file, step, sample);
+
+  /* Resizing must occur before writing beyond the end of file. Otherwise, the
+     data may get discarded if the supporting flexpage needs to be flushed. */
+
+  offset_t new_region = round(file_populated_span(&file), page(1));
+
+  printf("Resize to %ld...\n", new_region + file_populated_span(&file));
+
+  err = file_resize(&file, new_region + file_populated_span(&file));
+
+  if (err)
+  {
+    printf("Could not resize file: %s\n", l4sys_errtostr(err));
+    return 1;
+  }
+
+  printf("Resized file...\n");
+
+  /* Copy the sampled data to another file region. */
+
+  printf("Copy data to %ld...\n", new_region);
+
   for (unsigned long offset = 0; offset < file_populated_span(&file); offset += step)
   {
-    unsigned long remaining = file_populated_span(&file) - offset;
-    unsigned long sample_remaining = remaining < sample ? remaining : sample;
+    memcpy(file.memory + new_region + offset, file.memory + offset, sample);
+    if (step > sample)
+      memset(file.memory + new_region + offset + sample, 0, step - sample);
+  }
 
-    printf("%ld bytes from %p...\n", sample_remaining, (file.memory + offset));
-    strncpy(buf, (file.memory + offset), sample_remaining);
-    buf[sample_remaining] = '\0';
-    printf("%s\n", buf);
-  }
+  show(&file, step, sample);
+
+  printf("File shown.\n");
 
   return 0;
 }
diff -r 108c08c35100 -r 0073e2ca6c75 file.cc
--- a/file.cc	Wed Mar 17 00:10:47 2021 +0100
+++ b/file.cc	Thu Mar 18 00:59:55 2021 +0100
@@ -25,6 +25,7 @@
 #include <string.h>
 
 #include "dataspace_client.h"
+#include "file_client.h"
 #include "opener_client.h"
 #include "opener_context_client.h"
 #include "mapped_file_client.h"
@@ -128,6 +129,33 @@
   return ipc_attach_dataspace(file->ref, file_span(file), (void **) &file->memory);
 }
 
+/* Resize a file. */
+
+long file_resize(file_t *file, offset_t size)
+{
+  client_File _file(file->ref);
+  offset_t file_size = size;
+  long err = _file.resize(&file_size);
+
+  if (!err)
+  {
+    /* Determine the extent of the file in this region. */
+
+    if (file_size > file->end_pos)
+      file->data_end = file_span(file);
+    else
+      file->data_end = file_size - file->start_pos;
+
+    /* Update the file size locally. */
+
+    file->size = file_size;
+  }
+
+  return err;
+}
+
+
+
 /* Return the amount of data in the mapped region for the given file. */
 
 offset_t file_populated_span(file_t *file)
diff -r 108c08c35100 -r 0073e2ca6c75 file.h
--- a/file.h	Wed Mar 17 00:10:47 2021 +0100
+++ b/file.h	Thu Mar 18 00:59:55 2021 +0100
@@ -63,9 +63,13 @@
 long file_context_open(file_t *file, file_t *context);
 void file_init(file_t *file);
 
-/* File access region operations. */
+/* File and region operations. */
 
 long file_mmap(file_t *file, offset_t position, offset_t length);
+long file_resize(file_t *file, offset_t size);
+
+/* File and region properties. */
+
 offset_t file_populated_span(file_t *file);
 offset_t file_span(file_t *file);
 
diff -r 108c08c35100 -r 0073e2ca6c75 file_pager.cc
--- a/file_pager.cc	Wed Mar 17 00:10:47 2021 +0100
+++ b/file_pager.cc	Thu Mar 18 00:59:55 2021 +0100
@@ -24,6 +24,11 @@
     return Pager::flush(populated_size, size);
 }
 
+long FilePager::resize(offset_t *size)
+{
+    return Pager::resize(size);
+}
+
 long FilePager::mmap(offset_t position, offset_t length, offset_t *start_pos, offset_t *end_pos, offset_t *data_end)
 {
     /* Set the limits of the paged region. */
diff -r 108c08c35100 -r 0073e2ca6c75 file_pager.h
--- a/file_pager.h	Wed Mar 17 00:10:47 2021 +0100
+++ b/file_pager.h	Thu Mar 18 00:59:55 2021 +0100
@@ -25,6 +25,8 @@
 
     virtual long flush(offset_t populated_size, offset_t *size);
 
+    virtual long resize(offset_t *size);
+
     /* Pager and mapped file methods. */
 
     virtual long map(unsigned long offset, l4_addr_t hot_spot, flags_t flags, l4_snd_fpage_t *region);
diff -r 108c08c35100 -r 0073e2ca6c75 files/block_file_accessor.cc
--- a/files/block_file_accessor.cc	Wed Mar 17 00:10:47 2021 +0100
+++ b/files/block_file_accessor.cc	Thu Mar 18 00:59:55 2021 +0100
@@ -45,13 +45,44 @@
     fclose(fp);
 }
 
+/* Update the size of the file. */
+
+void BlockFileAccessor::set_size(offset_t size)
+{
+    void *new_data = realloc(_data, size);
+
+    if (new_data != NULL)
+    {
+        _data = (char *) new_data;
+
+        if (size > _size)
+            memset(_data + _size, 0, size - _size);
+
+        Accessor::set_size(size);
+    }
+}
+
 /* Data transfer methods. */
 
 void BlockFileAccessor::fill(Flexpage *flexpage)
 {
     offset_t filepos = flexpage->base_offset;
     offset_t addr = flexpage->base_addr;
-    offset_t populated_size = std::min(flexpage->size, _size - filepos);
+    offset_t populated_size;
+
+    /* Filling completely beyond the end of file should produce an empty
+       flexpage. This could potentially be a shared read-only flexpage that
+       would be replaced by an independent writable flexpage if ever written. */
+
+    if (filepos > _size)
+    {
+        memset((void *) addr, 0, flexpage->size);
+        return;
+    }
+
+    /* Otherwise, fill the populated portion of a flexpage. */
+
+    populated_size = std::min(flexpage->size, _size - filepos);
 
     /* Tag the region with file state. */
 
@@ -71,7 +102,17 @@
 {
     offset_t addr = flexpage->base_addr;
     offset_t filepos = flexpage->base_offset;
-    offset_t populated_size = std::min(flexpage->size, _size - filepos);
+    offset_t populated_size;
+
+    /* Flushing completely beyond the end of file should discard the
+       flexpage. */
+
+    if (filepos > _size)
+        return;
+
+    /* Otherwise, only the populated portion of a flexpage should be flushed. */
+
+    populated_size = std::min(flexpage->size, _size - filepos);
 
     /* Remove the file state tag from the region. */
 
diff -r 108c08c35100 -r 0073e2ca6c75 files/block_file_accessor.h
--- a/files/block_file_accessor.h	Wed Mar 17 00:10:47 2021 +0100
+++ b/files/block_file_accessor.h	Thu Mar 18 00:59:55 2021 +0100
@@ -13,6 +13,8 @@
 public:
     explicit BlockFileAccessor(const char *path, fileid_t fileid);
 
+    virtual void set_size(offset_t size);
+
     /* Data transfer methods. */
 
     virtual void fill(Flexpage *flexpage);
diff -r 108c08c35100 -r 0073e2ca6c75 pager.cc
--- a/pager.cc	Wed Mar 17 00:10:47 2021 +0100
+++ b/pager.cc	Thu Mar 18 00:59:55 2021 +0100
@@ -19,19 +19,19 @@
 
 long Pager::flush(offset_t populated_size, offset_t *size)
 {
-    offset_t limit = _start + populated_size;
-    offset_t file_size = _mapper->get_data_size();
+    _mapper->flush_all(_start, populated_size);
 
-    /* Extend the file if the populated size of the region goes beyond the
-       current size. */
+    *size = _mapper->get_data_size();
+    return L4_EOK;
+}
 
-    if (limit > file_size)
-    {
-        file_size = limit;
-        _mapper->set_data_size(file_size);
-    }
+/* Resize the underlying file. */
 
-    *size = file_size;
+long Pager::resize(offset_t *size)
+{
+    _mapper->set_data_size(*size);
+
+    *size = _mapper->get_data_size();
     return L4_EOK;
 }
 
diff -r 108c08c35100 -r 0073e2ca6c75 pager.h
--- a/pager.h	Wed Mar 17 00:10:47 2021 +0100
+++ b/pager.h	Thu Mar 18 00:59:55 2021 +0100
@@ -33,6 +33,8 @@
 
     virtual long flush(offset_t populated_size, offset_t *size);
 
+    virtual long resize(offset_t *size);
+
     /* Mapped file methods. */
 
     virtual long mmap(offset_t position, offset_t length, offset_t *start_pos, offset_t *end_pos, offset_t *data_end);