From c87f9627efc8b612eb9b000acfcc6731cad15765 Mon Sep 17 00:00:00 2001
From: Joel Klinghed <the_jk@spawned.biz>
Date: Tue, 7 Oct 2025 09:12:22 +0200
Subject: Initial commit

---
 test/io_test_helper.cc | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 test/io_test_helper.cc

(limited to 'test/io_test_helper.cc')

diff --git a/test/io_test_helper.cc b/test/io_test_helper.cc
new file mode 100644
index 0000000..9ac663a
--- /dev/null
+++ b/test/io_test_helper.cc
@@ -0,0 +1,82 @@
+#include "io_test_helper.hh"
+
+#include "io.hh"
+
+#include <algorithm>
+#include <cstddef>
+#include <expected>
+#include <memory>
+#include <utility>
+
+namespace {
+
+class BreakingReader : public io::Reader {
+ public:
+  BreakingReader(std::unique_ptr<io::Reader> reader, size_t offset,
+                 io::ReadError error)
+      : reader_(std::move(reader)), offset_(offset), error_(error) {}
+
+  [[nodiscard]]
+  std::expected<size_t, io::ReadError> read(void* dst, size_t max) override {
+    if (offset_ == 0)
+      return std::unexpected(error_);
+    size_t avail = std::min(offset_, max);
+    auto ret = reader_->read(dst, avail);
+    if (ret.has_value()) {
+      offset_ -= ret.value();
+    }
+    return ret;
+  }
+
+  [[nodiscard]]
+  std::expected<size_t, io::ReadError> skip(size_t max) override {
+    if (offset_ == 0)
+      return std::unexpected(error_);
+    size_t avail = std::min(offset_, max);
+    auto ret = reader_->skip(avail);
+    if (ret.has_value()) {
+      offset_ -= ret.value();
+    }
+    return ret;
+  }
+
+ private:
+  std::unique_ptr<io::Reader> reader_;
+  size_t offset_;
+  io::ReadError const error_;
+};
+
+class MaxBlockReader : public io::Reader {
+ public:
+  MaxBlockReader(std::unique_ptr<io::Reader> reader, size_t max_block_size)
+      : reader_(std::move(reader)), max_block_size_(max_block_size) {}
+
+  [[nodiscard]]
+  std::expected<size_t, io::ReadError> read(void* dst, size_t max) override {
+    size_t avail = std::min(max_block_size_, max);
+    return reader_->read(dst, avail);
+  }
+
+  [[nodiscard]]
+  std::expected<size_t, io::ReadError> skip(size_t max) override {
+    size_t avail = std::min(max_block_size_, max);
+    return reader_->skip(avail);
+  }
+
+ private:
+  std::unique_ptr<io::Reader> reader_;
+  size_t const max_block_size_;
+};
+
+}  // namespace
+
+std::unique_ptr<io::Reader> io_make_breaking(std::unique_ptr<io::Reader> reader,
+                                             size_t offset,
+                                             io::ReadError error) {
+  return std::make_unique<BreakingReader>(std::move(reader), offset, error);
+}
+
+std::unique_ptr<io::Reader> io_make_max_block(
+    std::unique_ptr<io::Reader> reader, size_t max_block_size) {
+  return std::make_unique<MaxBlockReader>(std::move(reader), max_block_size);
+}
-- 
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