From 15741411fbd21162f0ba06c55ddeadaf6efdd758 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <steinar+git@gunderson.no>
Date: Wed, 30 Sep 2020 21:20:33 +0200
Subject: [PATCH] Support building without io_uring.

This is pretty hackish! It would be nice to be able to switch to
meson, but TurboPFor makes that a bit tricky right now.
---
 Makefile            |  7 ++++++-
 io_uring_engine.cpp | 12 ++++++++++++
 io_uring_engine.h   |  5 +++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 3799b57..c51c41f 100644
--- a/Makefile
+++ b/Makefile
@@ -4,11 +4,16 @@ CXXFLAGS ?= -O2 -g -Wall -std=gnu++17
 CPPFLAGS=-ITurboPFor-Integer-Compression/
 INSTALL ?= install
 PREFIX ?= /usr/local
+URING_LIBS = $(shell pkg-config --libs liburing)
+
+ifeq ($(URING_LIBS),)
+  CPPFLAGS += -DWITHOUT_URING
+endif
 
 all: plocate plocate-build
 
 plocate: plocate.o io_uring_engine.o TurboPFor-Integer-Compression/libic.a
-	$(CXX) -o $@ $^ -lzstd $(shell pkg-config --libs liburing)
+	$(CXX) -o $@ $^ -lzstd $(URING_LIBS)
 
 plocate-build: plocate-build.o TurboPFor-Integer-Compression/libic.a
 	$(CXX) -o $@ $^ -lzstd
diff --git a/io_uring_engine.cpp b/io_uring_engine.cpp
index b10639d..7714cdb 100644
--- a/io_uring_engine.cpp
+++ b/io_uring_engine.cpp
@@ -1,5 +1,7 @@
 #include <string.h>
+#ifndef WITHOUT_URING
 #include <liburing.h>
+#endif
 #include <stdint.h>
 #include <unistd.h>
 #include <memory>
@@ -11,7 +13,11 @@ using namespace std;
 
 IOUringEngine::IOUringEngine()
 {
+#ifdef WITHOUT_URING
+	int ret = -1;
+#else
 	int ret = io_uring_queue_init(queue_depth, &ring, 0);
+#endif
 	using_uring = (ret >= 0);
 }
 
@@ -26,6 +32,7 @@ void IOUringEngine::submit_read(int fd, size_t len, off_t offset, function<void(
 		return;
 	}
 
+#ifndef WITHOUT_URING
 	if (pending_reads < queue_depth) {
 		io_uring_sqe *sqe = io_uring_get_sqe(&ring);
 		if (sqe == nullptr) {
@@ -36,8 +43,10 @@ void IOUringEngine::submit_read(int fd, size_t len, off_t offset, function<void(
 	} else {
 		queued_reads.push(QueuedRead{ fd, len, offset, move(cb) });
 	}
+#endif
 }
 
+#ifndef WITHOUT_URING
 void IOUringEngine::submit_read_internal(io_uring_sqe *sqe, int fd, size_t len, off_t offset, function<void(string)> cb)
 {
 	void *buf;
@@ -51,6 +60,7 @@ void IOUringEngine::submit_read_internal(io_uring_sqe *sqe, int fd, size_t len,
 	io_uring_sqe_set_data(sqe, pending);
 	++pending_reads;
 }
+#endif
 
 void IOUringEngine::finish()
 {
@@ -58,6 +68,7 @@ void IOUringEngine::finish()
 		return;
 	}
 
+#ifndef WITHOUT_URING
 	int ret = io_uring_submit(&ring);
 	if (ret < 0) {
 		fprintf(stderr, "io_uring_submit: %s\n", strerror(-ret));
@@ -133,6 +144,7 @@ void IOUringEngine::finish()
 			}
 		}
 	}
+#endif
 }
 
 void complete_pread(int fd, void *ptr, size_t len, off_t offset)
diff --git a/io_uring_engine.h b/io_uring_engine.h
index 93e7a0d..59a9d66 100644
--- a/io_uring_engine.h
+++ b/io_uring_engine.h
@@ -5,7 +5,10 @@
 #include <queue>
 #include <string>
 #include <stdint.h>
+#ifndef WITHOUT_URING
 #include <liburing.h>
+#endif
+#include <sys/socket.h>
 
 class IOUringEngine {
 public:
@@ -15,9 +18,11 @@ public:
 	size_t get_waiting_reads() const { return pending_reads + queued_reads.size(); }
 
 private:
+#ifndef WITHOUT_URING
 	void submit_read_internal(io_uring_sqe *sqe, int fd, size_t len, off_t offset, std::function<void(std::string)> cb);
 
 	io_uring ring;
+#endif
 	size_t pending_reads = 0;  // Number of requests we have going in the ring.
 	bool using_uring;
 
-- 
2.39.2