From d1a7f637975ac6b8d6017c3824a65e9a7910b23d Mon Sep 17 00:00:00 2001
From: xushiwei <x@goplus.org>
Date: Mon, 6 May 2024 13:26:09 +0800
Subject: [PATCH] demo: qsort

---
 README.md            |  3 ++-
 _demo/qsort/qsort.go | 17 +++++++++++++++++
 c/c.go               |  3 +++
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 _demo/qsort/qsort.go

diff --git a/README.md b/README.md
index 4cfc0868..b4b6e72b 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,8 @@ go install -v ./...
 
 The `_demo` directory contains our demos (it start with `_` to prevent the `go` command from compiling it):
 
-* genints: closure usage in llgo
+* [qsort](_demo/qsort): call C function with callback
+* [genints](_demo/genints): closure usage in llgo
 
 ### How to run demos
 
diff --git a/_demo/qsort/qsort.go b/_demo/qsort/qsort.go
new file mode 100644
index 00000000..95658371
--- /dev/null
+++ b/_demo/qsort/qsort.go
@@ -0,0 +1,17 @@
+package main
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+func main() {
+	a := [...]int{100, 8, 23, 2, 7}
+	c.Qsort(c.Pointer(&a), 5, unsafe.Sizeof(0), func(a, b c.Pointer) c.Int {
+		return c.Int(*(*int)(a) - *(*int)(b))
+	})
+	for _, v := range a {
+		c.Printf(c.Str("%d\n"), v)
+	}
+}
diff --git a/c/c.go b/c/c.go
index ac88b11a..340edd2c 100644
--- a/c/c.go
+++ b/c/c.go
@@ -71,3 +71,6 @@ func Printf(format *Char, __llgo_va_list ...any) Int
 
 //go:linkname Fprintf C.fprintf
 func Fprintf(fp FilePtr, format *Char, __llgo_va_list ...any) Int
+
+//go:linkname Qsort C.qsort
+func Qsort(base Pointer, count, elem uintptr, compar func(a, b Pointer) Int)