Implement a MOJO_READ_DATA_FLAG_PEEK flag for data pipes.
MOJO_READ_DATA_FLAG_PEEK allows the user to read data from a pipe
without removing it. The data will be available for the next read.
R=viettrungluu@chromium.org
Review URL: https://codereview.chromium.org/703573002
diff --git a/mojo/edk/system/core_unittest.cc b/mojo/edk/system/core_unittest.cc
index 9adde19..e6607df 100644
--- a/mojo/edk/system/core_unittest.cc
+++ b/mojo/edk/system/core_unittest.cc
@@ -1084,6 +1084,19 @@
EXPECT_EQ(MOJO_HANDLE_SIGNAL_READABLE, hss.satisfied_signals);
EXPECT_EQ(MOJO_HANDLE_SIGNAL_READABLE, hss.satisfiable_signals);
+ // Peek one character.
+ elements[0] = -1;
+ elements[1] = -1;
+ num_bytes = 1u;
+ EXPECT_EQ(MOJO_RESULT_OK,
+ core()->ReadData(
+ ch,
+ UserPointer<void>(elements),
+ MakeUserPointer(&num_bytes),
+ MOJO_READ_DATA_FLAG_NONE | MOJO_READ_DATA_FLAG_PEEK));
+ EXPECT_EQ('A', elements[0]);
+ EXPECT_EQ(-1, elements[1]);
+
// Read one character.
elements[0] = -1;
elements[1] = -1;
@@ -1131,6 +1144,16 @@
MOJO_READ_DATA_FLAG_QUERY));
EXPECT_EQ(4u, num_bytes);
+ // Try to query with peek. Should fail.
+ num_bytes = 0;
+ EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
+ core()->ReadData(
+ ch,
+ NullUserPointer(),
+ MakeUserPointer(&num_bytes),
+ MOJO_READ_DATA_FLAG_QUERY | MOJO_READ_DATA_FLAG_PEEK));
+ EXPECT_EQ(0u, num_bytes);
+
// Try to discard ten characters, in all-or-none mode. Should fail.
num_bytes = 10;
EXPECT_EQ(MOJO_RESULT_OUT_OF_RANGE,
@@ -1140,6 +1163,15 @@
MakeUserPointer(&num_bytes),
MOJO_READ_DATA_FLAG_DISCARD | MOJO_READ_DATA_FLAG_ALL_OR_NONE));
+ // Try to discard two characters, in peek mode. Should fail.
+ num_bytes = 2;
+ EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
+ core()->ReadData(
+ ch,
+ NullUserPointer(),
+ MakeUserPointer(&num_bytes),
+ MOJO_READ_DATA_FLAG_DISCARD | MOJO_READ_DATA_FLAG_PEEK));
+
// Discard two characters.
num_bytes = 2;
EXPECT_EQ(MOJO_RESULT_OK,
@@ -1149,9 +1181,17 @@
MakeUserPointer(&num_bytes),
MOJO_READ_DATA_FLAG_DISCARD | MOJO_READ_DATA_FLAG_ALL_OR_NONE));
- // Read the remaining two characters, in two-phase mode (all-or-none).
+ // Try a two-phase read of the remaining two bytes with peek. Should fail.
const void* read_ptr = nullptr;
num_bytes = 2;
+ ASSERT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
+ core()->BeginReadData(ch,
+ MakeUserPointer(&read_ptr),
+ MakeUserPointer(&num_bytes),
+ MOJO_READ_DATA_FLAG_PEEK));
+
+ // Read the remaining two characters, in two-phase mode (all-or-none).
+ num_bytes = 2;
ASSERT_EQ(MOJO_RESULT_OK,
core()->BeginReadData(ch,
MakeUserPointer(&read_ptr),
