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Preserve shortreal hierarchy width #10

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Preserve shortreal hierarchy width #10

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10 changes: 8 additions & 2 deletions fstcpp/fstcpp_writer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -126,16 +126,22 @@ Handle Writer::createVar(

// determine real/string handling like original C implementation
bool is_real{false};
uint32_t stored_bitwidth{bitwidth};
switch (vartype) {
case Hierarchy::VarType::VCD_REAL:
case Hierarchy::VarType::VCD_REAL_PARAMETER:
case Hierarchy::VarType::VCD_REALTIME:
case Hierarchy::VarType::SV_SHORTREAL:
is_real = true;
bitwidth = 8; // recast to double size
stored_bitwidth = bitwidth;
break;
case Hierarchy::VarType::SV_SHORTREAL:
is_real = true;
stored_bitwidth = 8;
break;
case Hierarchy::VarType::GEN_STRING:
bitwidth = 0;
stored_bitwidth = bitwidth;
break;
default:
break;
Expand Down Expand Up @@ -166,7 +172,7 @@ Handle Writer::createVar(
// I don't know why the original C implementation encode bitwidth again
const uint32_t geom_len{(bitwidth == 0 ? uint32_t(-1) : is_real ? uint32_t(0) : bitwidth)};
g.writeLEB128(geom_len);
m_value_change_data_.m_variable_infos.emplace_back(bitwidth, is_real);
m_value_change_data_.m_variable_infos.emplace_back(stored_bitwidth, is_real);
}

return alias_handle;
Expand Down
29 changes: 29 additions & 0 deletions fstcpp/fstcpp_writer_easy_blocks.test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,10 @@ class WriterTest : public ::testing::Test {
);
}

static const VariableInfo &getVariableInfo(Writer &writer, Handle handle) {
return writer.m_value_change_data_.m_variable_infos.at(handle - 1);
}

static void writeHeader(const Header &h, ostream &os) { Writer::writeHeader_(h, os); }

static void appendBlackout(Writer &Writer, std::ostream &os) { Writer.appendBlackout_(os); }
Expand Down Expand Up @@ -278,6 +282,31 @@ TEST_F(WriterTest, createVarVcdReal) {
EXPECT_EQ(buf, expected);
}

TEST_F(WriterTest, createVarSvShortreal) {
Writer writer;
writer.setWriterPackType(WriterPackType::NO_COMPRESSION);
const Handle handle{writer.createVar(
fst::Hierarchy::VarType::SV_SHORTREAL,
fst::Hierarchy::VarDirection::INPUT,
/*bitwidth =*/32,
"shortreal_val",
/*alias handle =*/0
)};
EXPECT_EQ(handle, 1u);

// Preserve the 32-bit shortreal width in the hierarchy.
const string hierarchy_buf{getHierarchyBuffer(writer)};
const string hierarchy_expected{"\x1d\x01shortreal_val\x00\x20\x00"s};
EXPECT_EQ(hierarchy_buf, hierarchy_expected);

// FST stores real values as doubles, including shortreal values promoted to double.
const string geometry_buf{getGeometryBuffer(writer)};
EXPECT_EQ(geometry_buf, "\x00"s);
const VariableInfo &variable_info{getVariableInfo(writer, handle)};
EXPECT_TRUE(variable_info.is_real());
EXPECT_EQ(variable_info.bitwidth(), 8u);
}

TEST_F(WriterTest, GeometryBufferNormalVar) {
Writer writer;
writer.setWriterPackType(WriterPackType::NO_COMPRESSION);
Expand Down
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