From bdc4a09356a61805958aa80d03691e5bbfe80565 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Sat, 23 Jan 2021 06:48:39 +1000
Subject: [PATCH] tools/analyse: use a deque to avoid expensive reallocations

We can amass a fair amount of allocated memory on some operations, so a
vector resize can exceed the available memory of a system on some
operations.
---
 tools/analyse.cpp | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/tools/analyse.cpp b/tools/analyse.cpp
index 7ddfdfa..a83a660 100644
--- a/tools/analyse.cpp
+++ b/tools/analyse.cpp
@@ -24,6 +24,7 @@
 #include <filesystem>
 #include <fstream>
 #include <iostream>
+#include <deque>
 
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -64,7 +65,7 @@ static bool region_equal (
 
 ///////////////////////////////////////////////////////////////////////////////
 static void find_path_chunks (
-    std::vector<emory::chunk::region> &res,
+    std::deque<emory::chunk::region> &res,
     std::filesystem::path const &src,
     emory::chunk::params const &p
 );
@@ -75,7 +76,7 @@ static void find_path_chunks (
 static
 void
 find_regular_chunks (
-    std::vector<emory::chunk::region> &res,
+    std::deque<emory::chunk::region> &res,
     std::filesystem::path const &src,
     emory::chunk::params const &p
 ) {
@@ -96,7 +97,7 @@ find_regular_chunks (
 static
 void
 find_directory_chunks (
-    std::vector<emory::chunk::region> &res,
+    std::deque<emory::chunk::region> &res,
     std::filesystem::path const &src,
     emory::chunk::params const &p
 ) {
@@ -111,7 +112,7 @@ find_directory_chunks (
 /// Scan chunks from a given path by dispatching to `find_foo_chunks` style
 /// functions depending on the file type.
 static void find_path_chunks (
-    std::vector<emory::chunk::region> &res,
+    std::deque<emory::chunk::region> &res,
     std::filesystem::path const &src,
     emory::chunk::params const &p
 ) {
@@ -139,12 +140,12 @@ static void find_path_chunks (
 
 
 ///----------------------------------------------------------------------------
-/// Find all regions in a path and return a vector of the regions.
+/// Find all regions in a path and return a container of the regions.
 static
-std::vector<emory::chunk::region>
+std::deque<emory::chunk::region>
 find_chunks (std::filesystem::path const &src, emory::chunk::params const &p)
 {
-    std::vector<emory::chunk::region> res;
+    std::deque<emory::chunk::region> res;
     find_path_chunks (res, src, p);
     return res;
 }
@@ -194,7 +195,7 @@ int main (int argc, char const **argv)
 
     // Find all the chunks and prepare them for output
     std::cout << "processing\n";
-    std::vector<emory::chunk::region> src = find_chunks (argv[ARGS_INPUT], p);
+    auto src = find_chunks (argv[ARGS_INPUT], p);
 
     fmt::print ("analysing {} chunks\n", src.size ());
     std::sort (src.begin (), src.end (), region_less);