From 32b41e5c60be45997e37b1ff879bc426bd00f15e Mon Sep 17 00:00:00 2001
From: Juan Cruz Viotti <jv@jviotti.com>
Date: Wed, 4 Mar 2026 09:22:47 -0400
Subject: [PATCH] Optimise I/O during indexing

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>
---
 src/build/adapter_filesystem.cc | 81 +++++++++++++++++++--------------
 src/index/index.cc              |  5 +-
 src/index/output.h              |  3 +-
 3 files changed, 50 insertions(+), 39 deletions(-)

diff --git a/src/build/adapter_filesystem.cc b/src/build/adapter_filesystem.cc
index bead7581..4aae8669 100644
--- a/src/build/adapter_filesystem.cc
+++ b/src/build/adapter_filesystem.cc
@@ -3,8 +3,9 @@
 #include <sourcemeta/core/io.h>
 
 #include <cassert>     // assert
-#include <fstream>     // std::ofstream
+#include <fstream>     // std::ofstream, std::ifstream
 #include <mutex>       // std::unique_lock
+#include <string>      // std::string
 #include <string_view> // std::string_view
 
 namespace sourcemeta::one {
@@ -25,45 +26,55 @@ auto BuildAdapterFilesystem::read_dependencies(const node_type &path) const
     -> std::optional<BuildDependencies<node_type>> {
   assert(path.is_absolute());
   const auto dependencies_path{this->dependencies_path(path)};
-  if (std::filesystem::exists(dependencies_path)) {
-    auto stream{sourcemeta::core::read_file(dependencies_path)};
-    assert(stream.is_open());
-
-    BuildDependencies<node_type> result;
-    std::string line;
-    while (std::getline(stream, line)) {
-      // Prevent CRLF on Windows
-      if (!line.empty() && line.back() == '\r') {
-        line.pop_back();
-      }
 
-      if (!line.empty()) {
-        auto kind{BuildDependencyKind::Static};
-        std::filesystem::path dependency;
-        if (line.size() >= 2 && line[1] == ' ' &&
-            (line[0] == 's' || line[0] == 'd')) {
-          kind = (line[0] == 'd') ? BuildDependencyKind::Dynamic
-                                  : BuildDependencyKind::Static;
-          dependency = line.substr(2);
-        } else {
-          dependency = line;
-        }
-        if (!dependency.is_absolute()) {
-          dependency =
-              std::filesystem::weakly_canonical(this->root / dependency);
-        }
-
-        result.emplace_back(kind, std::move(dependency));
-      }
+  std::ifstream stream{dependencies_path};
+  if (!stream.is_open()) {
+    return std::nullopt;
+  }
+
+  std::string contents{std::istreambuf_iterator<char>(stream),
+                       std::istreambuf_iterator<char>()};
+
+  BuildDependencies<node_type> result;
+  std::size_t position{0};
+  while (position < contents.size()) {
+    auto newline{contents.find('\n', position)};
+    if (newline == std::string::npos) {
+      newline = contents.size();
     }
 
-    if (result.empty()) {
-      return std::nullopt;
-    } else {
-      return result;
+    auto end{newline};
+    // Prevent CRLF on Windows
+    if (end > position && contents[end - 1] == '\r') {
+      end -= 1;
     }
-  } else {
+
+    if (end > position) {
+      auto kind{BuildDependencyKind::Static};
+      std::filesystem::path dependency;
+      const auto length{end - position};
+      if (length >= 2 && contents[position + 1] == ' ' &&
+          (contents[position] == 's' || contents[position] == 'd')) {
+        kind = (contents[position] == 'd') ? BuildDependencyKind::Dynamic
+                                           : BuildDependencyKind::Static;
+        dependency = contents.substr(position + 2, end - position - 2);
+      } else {
+        dependency = contents.substr(position, length);
+      }
+      if (!dependency.is_absolute()) {
+        dependency = (this->root / dependency).lexically_normal();
+      }
+
+      result.emplace_back(kind, std::move(dependency));
+    }
+
+    position = newline + 1;
+  }
+
+  if (result.empty()) {
     return std::nullopt;
+  } else {
+    return result;
   }
 }
 
diff --git a/src/index/index.cc b/src/index/index.cc
index 3e6d32af..cb039904 100644
--- a/src/index/index.cc
+++ b/src/index/index.cc
@@ -550,8 +550,9 @@ static auto index_main(const std::string_view &program,
     const auto relative_path{std::filesystem::relative(entry, schemas_path)};
     print_progress(mutex, 1, "Producing", relative_path.string(), cursor + 1,
                    directories.size());
-    const auto destination{std::filesystem::weakly_canonical(
-        explorer_path / relative_path / SENTINEL / "directory.metapack")};
+    const auto destination{
+        (explorer_path / relative_path / SENTINEL / "directory.metapack")
+            .lexically_normal()};
     DISPATCH<sourcemeta::one::GENERATE_EXPLORER_DIRECTORY_LIST>(
         destination,
         // If any of the entry summary files changes, by definition we need to
diff --git a/src/index/output.h b/src/index/output.h
index 384876f4..62e97874 100644
--- a/src/index/output.h
+++ b/src/index/output.h
@@ -16,8 +16,7 @@ namespace sourcemeta::one {
 
 class Output {
 public:
-  Output(std::filesystem::path path)
-      : path_{std::filesystem::weakly_canonical(path)} {
+  Output(std::filesystem::path path) : path_{path.lexically_normal()} {
     std::filesystem::create_directories(this->path_);
     for (const auto &entry :
          std::filesystem::recursive_directory_iterator(this->path_)) {