[Sys] Increased Read Buffers to Reduce Total Syscalls

This change was originally proposed by @heshpdx

See PR #2772

By increasing the read buffer, the number of syscalls can be reduced
since more of the large files are read per call.

libs/EXTERNAL/libblifparse/CMakeLists.txt

@@ -45,6 +45,10 @@ add_library(libblifparse STATIC
 target_include_directories(libblifparse PUBLIC ${LIB_INCLUDE_DIRS} ${CMAKE_CURRENT_BINARY_DIR})
 set_target_properties(libblifparse PROPERTIES PREFIX "") #Avoid extra 'lib' prefix
 
+# Set the read buffer size in the generated lexers. This reduces the number of
+# syscalls since the default is only 1kB.
+target_compile_definitions(libblifparse PRIVATE YY_READ_BUF_SIZE=1048576)
+
 #Create the test executable
 add_executable(blifparse_test src/main.cpp)
 target_link_libraries(blifparse_test libblifparse)

libs/libpugiutil/src/pugixml_loc.cpp

@@ -1,8 +1,14 @@
 #include <cstdio>
 #include <algorithm>
+#include <vector>
 #include "pugixml_util.hpp"
 #include "pugixml_loc.hpp"
 
+// The size of the read buffer when reading from a file.
+#ifndef PUGI_UTIL_READ_BUF_SIZE
+#define PUGI_UTIL_READ_BUF_SIZE 1048576
+#endif // PUGI_UTIL_READ_BUF_SIZE
+
 namespace pugiutil {
 
 //Return the line number from the given offset
@@ -30,10 +36,10 @@ void loc_data::build_loc_data() {
 
     std::ptrdiff_t offset = 0;
 
-    char buffer[1024];
+    std::vector<char> buffer(PUGI_UTIL_READ_BUF_SIZE);
     std::size_t size;
 
-    while ((size = fread(buffer, 1, sizeof(buffer), f)) > 0) {
+    while ((size = fread(buffer.data(), 1, buffer.size() * sizeof(char), f)) > 0) {
         for (std::size_t i = 0; i < size; ++i) {
             if (buffer[i] == '\n') {
                 offsets_.push_back(offset + i);

libs/libvtrutil/src/vtr_digest.cpp

@@ -3,10 +3,15 @@
 
 #include <iostream>
 #include <fstream>
-#include <array>
+#include <vector>
 
 #include "picosha2.h"
 
+// The size of the read buffer when reading from a file.
+#ifndef VTR_UTIL_READ_BUF_SIZE
+#define VTR_UTIL_READ_BUF_SIZE 1048576
+#endif // VTR_UTIL_READ_BUF_SIZE
+
 namespace vtr {
 
 std::string secure_digest_file(const std::string& filepath) {
@@ -21,7 +26,7 @@ std::string secure_digest_stream(std::istream& is) {
     //Read the stream in chunks and calculate the SHA256 digest
     picosha2::hash256_one_by_one hasher;
 
-    std::array<char, 1024> buf;
+    std::vector<char> buf(VTR_UTIL_READ_BUF_SIZE);
     while (!is.eof()) {
         //Process a chunk
         is.read(buf.data(), buf.size());