From a095a6169e71d804401f55eb828f0e3c9bb572e5 Mon Sep 17 00:00:00 2001
From: levlam <levlam@telegram.org>
Date: Tue, 31 Dec 2019 02:08:57 +0300
Subject: [PATCH] Better read_file implementation.

GitOrigin-RevId: 63c1911f53747a3d714e7a0265e9c354b5a70d3a
---
 tdutils/td/utils/Slice.h        |  8 ++++++
 tdutils/td/utils/filesystem.cpp | 48 ++++++++++++++++++---------------
 tdutils/td/utils/filesystem.h   |  2 +-
 3 files changed, 35 insertions(+), 23 deletions(-)

diff --git a/tdutils/td/utils/Slice.h b/tdutils/td/utils/Slice.h
index ae8da1b7a..3e350494d 100644
--- a/tdutils/td/utils/Slice.h
+++ b/tdutils/td/utils/Slice.h
@@ -308,4 +308,12 @@ inline MutableSlice as_slice(MutableSlice slice) {
   return slice;
 }
 
+inline Slice as_slice(const string &str) {
+  return str;
+}
+
+inline MutableSlice as_slice(string &str) {
+  return str;
+}
+
 }  // namespace td
diff --git a/tdutils/td/utils/filesystem.cpp b/tdutils/td/utils/filesystem.cpp
index c49c41261..888afb147 100644
--- a/tdutils/td/utils/filesystem.cpp
+++ b/tdutils/td/utils/filesystem.cpp
@@ -18,8 +18,23 @@
 
 namespace td {
 
-// TODO remove copypaste
-Result<BufferSlice> read_file(CSlice path, int64 size, int64 offset) {
+namespace {
+
+template <class T>
+T create_empty(size_t size);
+
+template <>
+string create_empty<string>(size_t size) {
+  return string(size, '\0');
+}
+
+template <>
+BufferSlice create_empty<BufferSlice>(size_t size) {
+  return BufferSlice{size};
+}
+
+template <class T>
+Result<T> read_file_impl(CSlice path, int64 size, int64 offset) {
   TRY_RESULT(from_file, FileFd::open(path, FileFd::Read));
   if (size == -1) {
     size = from_file.get_size();
@@ -31,7 +46,7 @@ Result<BufferSlice> read_file(CSlice path, int64 size, int64 offset) {
     return Status::Error("Failed to read file: invalid offset");
   }
   size -= offset;
-  BufferSlice content{narrow_cast<size_t>(size)};
+  auto content = create_empty<T>(narrow_cast<size_t>(size));
   TRY_RESULT(got_size, from_file.pread(as_slice(content), offset));
   if (got_size != static_cast<size_t>(size)) {
     return Status::Error("Failed to read file");
@@ -40,25 +55,14 @@ Result<BufferSlice> read_file(CSlice path, int64 size, int64 offset) {
   return std::move(content);
 }
 
-Result<std::string> read_file_str(CSlice path, int64 size, int64 offset) {
-  TRY_RESULT(from_file, FileFd::open(path, FileFd::Read));
-  if (size == -1) {
-    size = from_file.get_size();
-  }
-  if (size < 0) {
-    return Status::Error("Failed to read file: invalid size");
-  }
-  if (offset < 0 || offset > size) {
-    return Status::Error("Failed to read file: invalid offset");
-  }
-  size -= offset;
-  std::string content(narrow_cast<size_t>(size), '\0');
-  TRY_RESULT(got_size, from_file.pread(content, offset));
-  if (got_size != static_cast<size_t>(size)) {
-    return Status::Error("Failed to read file");
-  }
-  from_file.close();
-  return std::move(content);
+}  // namespace
+
+Result<BufferSlice> read_file(CSlice path, int64 size, int64 offset) {
+  return read_file_impl<BufferSlice>(path, size, offset);
+}
+
+Result<string> read_file_str(CSlice path, int64 size, int64 offset) {
+  return read_file_impl<string>(path, size, offset);
 }
 
 // Very straightforward function. Don't expect much of it.
diff --git a/tdutils/td/utils/filesystem.h b/tdutils/td/utils/filesystem.h
index afe420e5c..88be700af 100644
--- a/tdutils/td/utils/filesystem.h
+++ b/tdutils/td/utils/filesystem.h
@@ -13,7 +13,7 @@
 namespace td {
 
 Result<BufferSlice> read_file(CSlice path, int64 size = -1, int64 offset = 0);
-Result<std::string> read_file_str(CSlice path, int64 size = -1, int64 offset = 0);
+Result<string> read_file_str(CSlice path, int64 size = -1, int64 offset = 0);
 
 Status copy_file(CSlice from, CSlice to, int64 size = -1) TD_WARN_UNUSED_RESULT;