From 1a9358e84b86ca2374521d99c44ab65fc934d725 Mon Sep 17 00:00:00 2001
From: Vladimir Chalupecky <vladimir.chalupecky@gmail.com>
Date: Mon, 28 Nov 2016 00:00:20 +0100
Subject: [PATCH] native,cgo: add error checking to Dlaswp and update docs

---
 cgo/lapack.go     | 29 +++++++++++++++++++++++++----
 native/dlaswp.go  | 29 ++++++++++++++++++++++++-----
 native/general.go |  4 +++-
 3 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/cgo/lapack.go b/cgo/lapack.go
index b2d861d0..694d3d77 100644
--- a/cgo/lapack.go
+++ b/cgo/lapack.go
@@ -28,8 +28,10 @@ const (
 	badHowMany      = "lapack: bad HowMany"
 	badIlo          = "lapack: ilo out of range"
 	badIhi          = "lapack: ihi out of range"
-	badIpiv         = "lapack: insufficient permutation length"
+	badIpiv         = "lapack: bad permutation length"
 	badJob          = "lapack: bad Job"
+	badK1           = "lapack: k1 out of range"
+	badK2           = "lapack: k2 out of range"
 	badKperm        = "lapack: incorrect permutation length"
 	badLdA          = "lapack: index of a out of range"
 	badNorm         = "lapack: bad norm"
@@ -511,12 +513,31 @@ func (impl Implementation) Dlasrt(s lapack.Sort, n int, d []float64) {
 	lapacke.Dlasrt(byte(s), n, d[:n])
 }
 
-// Dlaswp swaps the rows k1 to k2 of a according to the indices in ipiv.
-// a is a matrix with n columns and stride lda. incX is the increment for ipiv.
-// k1 and k2 are zero-indexed. If incX is negative, then loops from k2 to k1
+// Dlaswp swaps the rows k1 to k2 of a rectangular matrix A according to the
+// indices in ipiv so that row k is swapped with ipiv[k].
+//
+// n is the number of columns of A and incX is the increment for ipiv. If incX
+// is 1, the swaps are applied from k1 to k2. If incX is -1, the swaps are
+// applied in reverse order from k2 to k1. For other values of incX Dlaswp will
+// panic. ipiv must have length k2+1, otherwise Dlaswp will panic.
+//
+// The indices k1, k2, and the elements of ipiv are zero-based.
 //
 // Dlaswp is an internal routine. It is exported for testing purposes.
 func (impl Implementation) Dlaswp(n int, a []float64, lda, k1, k2 int, ipiv []int, incX int) {
+	switch {
+	case n < 0:
+		panic(nLT0)
+	case k2 < 0:
+		panic(badK2)
+	case k1 < 0 || k2 < k1:
+		panic(badK1)
+	case len(ipiv) != k2+1:
+		panic(badIpiv)
+	case incX != 1 && incX != -1:
+		panic(absIncNotOne)
+	}
+
 	ipiv32 := make([]int32, len(ipiv))
 	for i, v := range ipiv {
 		ipiv32[i] = int32(v + 1)
diff --git a/native/dlaswp.go b/native/dlaswp.go
index 26d09b81..1eee3057 100644
--- a/native/dlaswp.go
+++ b/native/dlaswp.go
@@ -6,15 +6,34 @@ package native
 
 import "github.com/gonum/blas/blas64"
 
-// Dlaswp swaps the rows k1 to k2 of a according to the indices in ipiv.
-// a is a matrix with n columns and stride lda. incX is the increment for ipiv.
-// k1 and k2 are zero-indexed. If incX is negative, then loops from k2 to k1
+// Dlaswp swaps the rows k1 to k2 of a rectangular matrix A according to the
+// indices in ipiv so that row k is swapped with ipiv[k].
+//
+// n is the number of columns of A and incX is the increment for ipiv. If incX
+// is 1, the swaps are applied from k1 to k2. If incX is -1, the swaps are
+// applied in reverse order from k2 to k1. For other values of incX Dlaswp will
+// panic. ipiv must have length k2+1, otherwise Dlaswp will panic.
+//
+// The indices k1, k2, and the elements of ipiv are zero-based.
 //
 // Dlaswp is an internal routine. It is exported for testing purposes.
-func (impl Implementation) Dlaswp(n int, a []float64, lda, k1, k2 int, ipiv []int, incX int) {
-	if incX != 1 && incX != -1 {
+func (impl Implementation) Dlaswp(n int, a []float64, lda int, k1, k2 int, ipiv []int, incX int) {
+	switch {
+	case n < 0:
+		panic(nLT0)
+	case k2 < 0:
+		panic(badK2)
+	case k1 < 0 || k2 < k1:
+		panic(badK1)
+	case len(ipiv) != k2+1:
+		panic(badIpiv)
+	case incX != 1 && incX != -1:
 		panic(absIncNotOne)
 	}
+
+	if n == 0 {
+		return
+	}
 	bi := blas64.Implementation()
 	if incX == 1 {
 		for k := k1; k <= k2; k++ {
diff --git a/native/general.go b/native/general.go
index e41a16f1..cd43c42d 100644
--- a/native/general.go
+++ b/native/general.go
@@ -32,8 +32,10 @@ const (
 	badHowMany      = "lapack: bad HowMany"
 	badIlo          = "lapack: ilo out of range"
 	badIhi          = "lapack: ihi out of range"
-	badIpiv         = "lapack: insufficient permutation length"
+	badIpiv         = "lapack: bad permutation length"
 	badJob          = "lapack: bad Job"
+	badK1           = "lapack: k1 out of range"
+	badK2           = "lapack: k2 out of range"
 	badKperm        = "lapack: incorrect permutation length"
 	badLdA          = "lapack: index of a out of range"
 	badNorm         = "lapack: bad norm"