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Diffstat (limited to 'internal/stupidgcm/stupidgcm.go')
-rw-r--r--internal/stupidgcm/stupidgcm.go16
1 files changed, 15 insertions, 1 deletions
diff --git a/internal/stupidgcm/stupidgcm.go b/internal/stupidgcm/stupidgcm.go
index 54915df..d690f93 100644
--- a/internal/stupidgcm/stupidgcm.go
+++ b/internal/stupidgcm/stupidgcm.go
@@ -139,7 +139,18 @@ func (g stupidGCM) Open(dst, iv, in, authData []byte) ([]byte, error) {
if len(in) <= tagLen {
log.Panic("Input data too short")
}
- buf := make([]byte, len(in)-tagLen)
+
+ // If the "dst" slice is large enough we can use it as our output buffer
+ outLen := len(in) - tagLen
+ var buf []byte
+ inplace := false
+ if cap(dst)-len(dst) >= outLen {
+ inplace = true
+ buf = dst[len(dst) : len(dst)+outLen]
+ } else {
+ buf = make([]byte, len(in)-tagLen)
+ }
+
ciphertext := in[:len(in)-tagLen]
tag := in[len(in)-tagLen:]
@@ -207,5 +218,8 @@ func (g stupidGCM) Open(dst, iv, in, authData []byte) ([]byte, error) {
return nil, ErrAuth
}
+ if inplace {
+ return dst[:len(dst)+outLen], nil
+ }
return append(dst, buf...), nil
}