From 62956a6b138c3824389274cee87a9f781ff4077c Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Mon, 8 Jun 2020 22:32:53 -0400
Subject: init

---
 .gitignore |   1 +
 Cargo.lock |  23 +++++++++++++
 Cargo.toml |  20 +++++++++++
 src/lib.rs | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 159 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 src/lib.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..5837ea0
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,23 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "build_const"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39092a32794787acd8525ee150305ff051b0aa6cc2abaf193924f5ab05425f39"
+
+[[package]]
+name = "crc"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d663548de7f5cca343f1e0a48d14dcfb0e9eb4e079ec58883b7251539fa10aeb"
+dependencies = [
+ "build_const",
+]
+
+[[package]]
+name = "growth-ring"
+version = "0.1.0"
+dependencies = [
+ "crc",
+]
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..0899509
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "growth-ring"
+version = "0.1.0"
+authors = ["Determinant <tederminant@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+crc = "1.8.1"
+
+[lib]
+name = "growthring"
+path = "src/lib.rs"
+crate-type = ["dylib", "rlib", "staticlib"]
+
+
+[profile.release]
+lto = true
+debug = true
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..d6a1e12
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,115 @@
+#[repr(u8)]
+enum WALRingType {
+    Full,
+    First,
+    Middle,
+    Last
+}
+
+struct WALRingBlob {
+    crc32: u32,
+    rsize: u32,
+    rtype: WALRingType,
+    // payload follows
+}
+
+type WALFileId = u32;
+type WALPos = u64;
+type WALWrite = (WALPos, Box<[u8]>);
+
+pub struct WALState {
+    pub base: WALPos,
+    pub last: WALPos,
+    pub block_nbit: u8,
+    pub file_nbit: u8,
+}
+
+pub struct WALWriter {
+    state: WALState,
+    block_buffer: Box<[u8]>,
+    block_size: u32,
+    file_size: u64,
+}
+
+impl WALWriter {
+    pub fn new(state: WALState) -> Self {
+        let mut b = Vec::new();
+        let block_size = 1 << (state.block_nbit as u32);
+        let file_size = 1 << (state.file_nbit as u64);
+        b.resize(block_size as usize, 0);
+        WALWriter{
+            state,
+            block_buffer: b.into_boxed_slice(),
+            block_size,
+            file_size,
+        }
+    }
+
+    pub fn grow(&mut self, records: &[Box<[u8]>]) -> Vec<WALWrite> {
+        let mut res = Vec::new();
+        let msize = std::mem::size_of::<WALRingBlob>() as u32;
+        // the global offest of the begining of the block
+        // the start of the unwritten data
+        let mut bbuff_start = self.state.last as u32 & (self.block_size - 1);
+        // the end of the unwritten data
+        let mut bbuff_cur = bbuff_start;
+
+        for _rec in records {
+            let mut rec = &_rec[..];
+            let mut rsize = rec.len() as u32;
+            let mut started = false;
+            while rsize > 0 {
+                let remain = self.block_size - bbuff_cur;
+                if remain > msize {
+                    let d = remain - msize;
+                    let blob = unsafe {std::mem::transmute::<*mut u8, &mut WALRingBlob>(
+                        &mut self.block_buffer[bbuff_cur as usize] as *mut u8)};
+                    if d >= rsize {
+                        // the remaining rec fits in the block
+                        let payload = rec;
+                        blob.crc32 = crc::crc32::checksum_ieee(payload);
+                        blob.rsize = rsize;
+                        blob.rtype = if started {WALRingType::Last} else {WALRingType::Full};
+                        rsize = 0;
+                        &mut self.block_buffer[bbuff_cur as usize..].copy_from_slice(payload);
+                        bbuff_cur += rsize;
+                    } else {
+                        // the remaining block can only accommodate partial rec
+                        let payload = &rec[..d as usize];
+                        blob.crc32 = crc::crc32::checksum_ieee(payload);
+                        blob.rsize = d;
+                        blob.rtype = if started {WALRingType::Middle} else {
+                            started = true;
+                            WALRingType::First
+                        };
+                        rsize -= d;
+                        &mut self.block_buffer[bbuff_cur as usize..].copy_from_slice(payload);
+                        bbuff_cur += d;
+                        rec = &rec[d as usize..];
+                    }
+                } else {
+                    // add padding space by moving the point to the end of the block
+                    bbuff_cur = self.block_size;
+                }
+                if bbuff_cur == self.block_size {
+                    res.push((self.state.last,
+                             self.block_buffer[bbuff_start as usize..]
+                                .to_vec().into_boxed_slice()));
+                    self.state.last += (self.block_size - bbuff_start) as u64;
+                    bbuff_start = 0;
+                    bbuff_cur = 0;
+                }
+            }
+        }
+        if bbuff_cur > bbuff_start {
+            res.push((self.state.last,
+                     self.block_buffer[bbuff_start as usize..bbuff_cur as usize]
+                        .to_vec().into_boxed_slice()));
+            self.state.last += (bbuff_cur - bbuff_start) as u64;
+        }
+        res
+    }
+}
+
+struct WALReader {
+}
-- 
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