diff --git a/loadsig/loadsig/src/hspice.rs b/loadsig/loadsig/src/hspice.rs
index f4b168d..728b683 100644
--- a/loadsig/loadsig/src/hspice.rs
+++ b/loadsig/loadsig/src/hspice.rs
@@ -1,6 +1,7 @@
 use super::shared::{self, Endian};
 use byteorder::ReadBytesExt;
 use std::io::{Read, Seek, SeekFrom};
+use std::str::FromStr;
 use thiserror::Error as TeError;
 
 // Reference:
@@ -14,13 +15,11 @@ use thiserror::Error as TeError;
 pub enum Error {
     #[error("IO error {0}")]
     Io(#[from] std::io::Error),
-    #[error(
-        "fail to cast value into integral value. this usually caused by some value out of range"
-    )]
+    #[error("fail to cast value into integral value. maybe some values out of range")]
     CastToInt(#[from] std::num::TryFromIntError),
     #[error("something was overflow")]
     Overflow,
-    #[error("wrong endian integer {0:#X} in block head. it must be one of 0x4 or 0x4000000")]
+    #[error("wrong endian integer {0:#X} in block head. it must be one of 0x4 or 0x04000000")]
     WrongEndianInt(u32),
     #[error("wrong block head value {0:#X}. it must be 0x4")]
     WrongBlockHead(u32),
@@ -31,10 +30,6 @@ pub enum Error {
 }
 type Result<T> = std::result::Result<T, Error>;
 
-const ENDIAN_INT: u32 = 0x4;
-const LITTLE_ENDIAN_INT: u32 = 0x4;
-const BIG_ENDIAN_INT: u32 = 0x4000000;
-
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum SimSource {
     /// For HSPICE, read as big endian.
@@ -51,14 +46,16 @@ impl SimSource {
     }
 }
 
-pub struct HSpiceData {}
+const ENDIAN_INT: u32 = 0x4;
+const LITTLE_ENDIAN_INT: u32 = 0x4;
+const BIG_ENDIAN_INT: u32 = 0x04000000;
 
 #[derive(Debug)]
-struct HspiceBlock {
+struct HSpiceBlock {
     block_offset: u64,
     block_len: u32,
 }
-impl HspiceBlock {
+impl HSpiceBlock {
     pub fn new(block_offset: u64, block_len: u32) -> Self {
         Self {
             block_offset,
@@ -74,46 +71,86 @@ impl HspiceBlock {
     }
 }
 #[derive(Debug)]
-struct HspiceBlocks {
+struct HSpiceBlocks {
     sim_source: SimSource,
-    blocks: Vec<HspiceBlock>,
-    header_blk_cnt: usize,
+    blocks: Vec<HSpiceBlock>,
 }
-impl HspiceBlocks {
-    pub fn new(sim_source: SimSource, blocks: Vec<HspiceBlock>, header_blk_cnt: usize) -> Self {
-        Self {
-            sim_source,
-            blocks,
-            header_blk_cnt,
+impl HSpiceBlocks {
+    pub fn new<T>(reader: &mut T) -> Result<Self>
+    where
+        T: ReadBytesExt + Seek,
+    {
+        // Back to the file head
+        reader.rewind()?;
+
+        // Fetch the first u32 as little endian to decide the sim source
+        let endian_u32 = shared::read_int_value(Endian::LittleEndian, reader)?;
+        let sim_source = match endian_u32 {
+            LITTLE_ENDIAN_INT => SimSource::HspiceWin,
+            BIG_ENDIAN_INT => SimSource::Hspice,
+            other => return Err(Error::WrongEndianInt(other)),
+        };
+        let endian = sim_source.to_endian();
+
+        // Iterate each block
+        let mut blocks: Vec<HSpiceBlock> = Vec::new();
+        reader.rewind()?;
+        loop {
+            // Read block header.
+            // If there is no more data, break this loop.
+            let mut block_header = [0u32; 4];
+            if let Err(e) = shared::read_int_values(endian, &mut block_header, reader) {
+                match e.kind() {
+                    std::io::ErrorKind::UnexpectedEof => break,
+                    _ => return Err(e.into()),
+                }
+            }
+
+            // Check endian u32
+            if block_header[0] != ENDIAN_INT {
+                return Err(Error::WrongBlockHead(block_header[0]));
+            }
+            if block_header[2] != ENDIAN_INT {
+                return Err(Error::WrongBlockHead(block_header[2]));
+            }
+
+            // Get the offset and length of block body
+            let block_offset = reader.stream_position()?;
+            let block_len = block_header[3];
+
+            // Skip block body to check block tail
+            reader.seek(SeekFrom::Current(i64::try_from(block_len).unwrap()))?;
+            let block_tail = shared::read_int_value(endian, reader)?;
+            if block_tail != block_len {
+                return Err(Error::WrongBlockTail(block_tail, block_len));
+            }
+
+            // Push result
+            blocks.push(HSpiceBlock::new(block_offset, block_len));
+
+            // Cursor now at the beginning of next block.
+            // We can continue analyze next blocks safely.
         }
+
+        // Build result and return.
+        Ok(Self { sim_source, blocks })
     }
 }
-impl<'a> HspiceBlocks {
-    pub fn to_reader<T>(&'a self, reader: T) -> HspiceBlocksReader<'a, T>
+impl<'a> HSpiceBlocks {
+    pub fn to_reader<T>(&'a self, reader: T) -> HSpiceBlocksReader<'a, T>
     where
         T: Read + Seek,
     {
-        HspiceBlocksReader::new(reader, &self.blocks)
-    }
-    pub fn to_header_reader<T>(&'a self, reader: T) -> HspiceBlocksReader<'a, T>
-    where
-        T: Read + Seek,
-    {
-        HspiceBlocksReader::new(reader, &self.blocks[..self.header_blk_cnt])
-    }
-    pub fn to_data_reader<T>(&'a self, reader: T) -> HspiceBlocksReader<'a, T>
-    where
-        T: Read + Seek,
-    {
-        HspiceBlocksReader::new(reader, &self.blocks[self.header_blk_cnt..])
+        HSpiceBlocksReader::new(reader, &self.blocks)
     }
 }
-struct HspiceBlocksReader<'a, T>
+
+struct HSpiceBlocksReader<'a, T>
 where
     T: Read + Seek,
 {
     reader: T,
-    blocks: &'a [HspiceBlock],
+    blocks: &'a [HSpiceBlock],
 
     /// The full size of this reader
     total_len: u64,
@@ -126,11 +163,11 @@ where
     /// The cursor inside block.
     cursor: u32,
 }
-impl<'a, T> HspiceBlocksReader<'a, T>
+impl<'a, T> HSpiceBlocksReader<'a, T>
 where
     T: Read + Seek,
 {
-    pub fn new(reader: T, blocks: &'a [HspiceBlock]) -> Self {
+    pub fn new(reader: T, blocks: &'a [HSpiceBlock]) -> Self {
         // Build total length and offset table.
         let mut total_len: u64 = 0;
         let mut offset_table: Vec<u64> = Vec::with_capacity(blocks.len());
@@ -142,7 +179,7 @@ where
         // otherwise Seek impl will panic when SeekFrom::Current.
         offset_table.push(total_len);
 
-        HspiceBlocksReader {
+        HSpiceBlocksReader {
             reader,
             blocks,
             total_len,
@@ -155,7 +192,7 @@ where
         self.reader
     }
 }
-impl<'a, T> Read for HspiceBlocksReader<'a, T>
+impl<'a, T> Read for HSpiceBlocksReader<'a, T>
 where
     T: Read + Seek,
 {
@@ -213,7 +250,7 @@ where
         }
     }
 }
-impl<'a, T> Seek for HspiceBlocksReader<'a, T>
+impl<'a, T> Seek for HSpiceBlocksReader<'a, T>
 where
     T: Read + Seek,
 {
@@ -269,6 +306,46 @@ where
     }
 }
 
+const SIGNAL_NAME_LEN: usize = 8;
+const SIGNAL_NAME_MAGIC_TAIL: &[u8; 4] = b"$&%#";
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum HSpiceVersion {
+    V9007,
+    V9601,
+    V2001,
+}
+#[derive(Debug, TeError)]
+#[error("can not parse given string into valid HSpice version")]
+pub struct ParseHSpiceVersionError {}
+impl FromStr for HSpiceVersion {
+    type Err = ParseHSpiceVersionError;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        match s {
+            "9007" => Ok(Self::V9007),
+            "9601" => Ok(Self::V9601),
+            "2001" => Ok(Self::V2001),
+            _ => Err(ParseHSpiceVersionError {}),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct HSpiceDigest {
+    version: HSpiceVersion,
+    file_name: String,
+    timestamp: String,
+    copyright: String,
+}
+
+#[derive(Debug)]
+pub struct HSpiceContent {
+    digest: HSpiceDigest,
+}
+
+pub type HSpiceData = HSpiceContent;
+
 /// Guess whether given reader is a legal HSPICE signal file.
 ///
 /// Please note that this is a vauge check.
@@ -294,102 +371,9 @@ where
 }
 
 /// Load given reader as HSPICE signal file.
-pub fn load_signal<T>(reader: &mut T) -> Result<HSpiceData>
+pub fn load_signal<T>(reader: T) -> Result<HSpiceData>
 where
     T: ReadBytesExt + Seek,
 {
-    // Fetch blocks list first
-    let blocks = analyze_hspice_block(reader)?;
-    println!("{:#?}", blocks);
-
-    Ok(HSpiceData {})
+    Err(Error::Overflow)
 }
-
-fn analyze_hspice_block<T>(reader: &mut T) -> Result<HspiceBlocks>
-where
-    T: ReadBytesExt + Seek,
-{
-    // Back to the file head
-    reader.rewind()?;
-
-    // Fetch the first u32 as little endian to decide the sim source
-    let endian_u32 = shared::read_int_value(Endian::LittleEndian, reader)?;
-    let sim_source = match endian_u32 {
-        LITTLE_ENDIAN_INT => SimSource::HspiceWin,
-        BIG_ENDIAN_INT => SimSource::Hspice,
-        other => return Err(Error::WrongEndianInt(other)),
-    };
-    let endian = sim_source.to_endian();
-
-    // Iterate each block
-    let mut blocks: Vec<HspiceBlock> = Vec::new();
-    reader.rewind()?;
-    loop {
-        // Read block header.
-        // If there is no more data, break this loop.
-        let mut block_header = [0u32; 4];
-        if let Err(e) = shared::read_int_values(endian, &mut block_header, reader) {
-            match e.kind() {
-                std::io::ErrorKind::UnexpectedEof => break,
-                _ => return Err(e.into()),
-            }
-        }
-
-        // Check endian u32
-        if block_header[0] != ENDIAN_INT {
-            return Err(Error::WrongBlockHead(block_header[0]));
-        }
-        if block_header[2] != ENDIAN_INT {
-            return Err(Error::WrongBlockHead(block_header[2]));
-        }
-
-        // Get the offset and length of block body
-        let block_offset = reader.stream_position()?;
-        let block_len = block_header[3];
-
-        // Skip block body to check block tail
-        reader.seek(SeekFrom::Current(i64::try_from(block_len).unwrap()))?;
-        let block_tail = shared::read_int_value(endian, reader)?;
-        if block_tail != block_len {
-            return Err(Error::WrongBlockTail(block_tail, block_len));
-        }
-
-        // Push result
-        blocks.push(HspiceBlock::new(block_offset, block_len));
-
-        // Cursor now at the beginning of next block.
-        // We can continue analyze next blocks safely.
-    }
-
-    // Analyze header block count
-    let mut header_blk_cnt: Option<usize> = None;
-    for (i, block) in blocks.iter().enumerate() {
-        let signal_name_len = u32::try_from(SIGNAL_NAME_LEN).unwrap();
-        let offset = if block.block_len < signal_name_len {
-            continue;
-        } else {
-            block.compute_offset(block.block_len - signal_name_len)
-        };
-
-        reader.seek(SeekFrom::Start(offset))?;
-        let mut magic_word = [0u8; MAGIC_WORDS.len()];
-        reader.read_exact(&mut magic_word)?;
-        if &magic_word == MAGIC_WORDS {
-            match i.checked_add(1) {
-                Some(v) => header_blk_cnt = Some(v),
-                None => return Err(Error::Overflow),
-            }
-            break;
-        }
-    }
-    let header_blk_cnt = match header_blk_cnt {
-        Some(v) => v,
-        None => return Err(Error::NoMagicWords),
-    };
-
-    // Build result and return.
-    Ok(HspiceBlocks::new(sim_source, blocks, header_blk_cnt))
-}
-
-const SIGNAL_NAME_LEN: usize = 8;
-const MAGIC_WORDS: &[u8; 4] = b"$&%#";
diff --git a/loadsig/loadsig/src/lib.rs b/loadsig/loadsig/src/lib.rs
index 9fdfbe3..cfee6d0 100644
--- a/loadsig/loadsig/src/lib.rs
+++ b/loadsig/loadsig/src/lib.rs
@@ -71,13 +71,13 @@ pub enum SpiceData {
     NgSpice(ngspice::NgSpiceData),
 }
 
-pub fn load_signal<T>(reader: &mut T) -> Result<SpiceData>
+pub fn load_signal<T>(mut reader: T) -> Result<SpiceData>
 where
     T: ReadBytesExt + Seek,
 {
-    if ngspice::guess_signal(reader) {
+    if ngspice::guess_signal(&mut reader) {
         Ok(SpiceData::NgSpice(ngspice::load_signal(reader)?))
-    } else if hspice::guess_signal(reader) {
+    } else if hspice::guess_signal(&mut reader) {
         Ok(SpiceData::HSpice(hspice::load_signal(reader)?))
     } else {
         Err(Error::InvalidFmt)
diff --git a/loadsig/loadsig/src/ngspice.rs b/loadsig/loadsig/src/ngspice.rs
index 3851c2e..7031327 100644
--- a/loadsig/loadsig/src/ngspice.rs
+++ b/loadsig/loadsig/src/ngspice.rs
@@ -25,7 +25,7 @@ where
 }
 
 /// Load given reader as HSPICE signal file.
-pub fn load_signal<T>(reader: &mut T) -> Result<NgSpiceData>
+pub fn load_signal<T>(reader: T) -> Result<NgSpiceData>
 where
     T: ReadBytesExt + Seek,
 {
diff --git a/loadsig/loadsig_exe/src/main.rs b/loadsig/loadsig_exe/src/main.rs
index a8dd0a1..41325f3 100644
--- a/loadsig/loadsig_exe/src/main.rs
+++ b/loadsig/loadsig_exe/src/main.rs
@@ -14,11 +14,11 @@ struct LoadSigArgs {
 fn main() {
     let args = LoadSigArgs::parse();
 
-    let mut reader = std::fs::File::open(&args.input).unwrap_or_else(|e| {
+    let reader = std::fs::File::open(&args.input).unwrap_or_else(|e| {
         eprintln!("{}", e);
         std::process::exit(1);
     });
-    let _ = loadsig::load_signal(&mut reader).unwrap_or_else(|e| {
+    let _ = loadsig::load_signal(reader).unwrap_or_else(|e| {
         eprintln!("{}", e);
         std::process::exit(2);
     });