From 2b0193e6bffae54a02cc09a4621b0e2bdd565947 Mon Sep 17 00:00:00 2001
From: anastasia <lubennikovaav@gmail.com>
Date: Fri, 4 Jun 2021 15:46:47 +0300
Subject: [PATCH] implement from_bytes for XLogPageHeader structs

---
 pageserver/src/waldecoder.rs   | 40 ++++------------------------------
 postgres_ffi/src/xlog_utils.rs | 26 ++++++++++++++++++++++
 2 files changed, 30 insertions(+), 36 deletions(-)

diff --git a/pageserver/src/waldecoder.rs b/pageserver/src/waldecoder.rs
index a3d17a0f9c..3d589b89c0 100644
--- a/pageserver/src/waldecoder.rs
+++ b/pageserver/src/waldecoder.rs
@@ -79,7 +79,8 @@ impl WalStreamDecoder {
                     return Ok(None);
                 }
 
-                let hdr = self.decode_XLogLongPageHeaderData();
+                let hdr = XLogLongPageHeaderData::from_bytes(&mut self.inputbuf);
+
                 if hdr.std.xlp_pageaddr != self.lsn.0 {
                     return Err(WalDecodeError {
                         msg: "invalid xlog segment header".into(),
@@ -95,7 +96,8 @@ impl WalStreamDecoder {
                     return Ok(None);
                 }
 
-                let hdr = self.decode_XLogPageHeaderData();
+                let hdr = XLogPageHeaderData::from_bytes(&mut self.inputbuf);
+
                 if hdr.xlp_pageaddr != self.lsn.0 {
                     return Err(WalDecodeError {
                         msg: "invalid xlog page header".into(),
@@ -184,40 +186,6 @@ impl WalStreamDecoder {
 
         // deal with xlog_switch records
     }
-
-    #[allow(non_snake_case)]
-    fn decode_XLogPageHeaderData(&mut self) -> XLogPageHeaderData {
-        let buf = &mut self.inputbuf;
-
-        // FIXME: Assume little-endian
-
-        let hdr: XLogPageHeaderData = XLogPageHeaderData {
-            xlp_magic: buf.get_u16_le(),
-            xlp_info: buf.get_u16_le(),
-            xlp_tli: buf.get_u32_le(),
-            xlp_pageaddr: buf.get_u64_le(),
-            xlp_rem_len: buf.get_u32_le(),
-        };
-        // 4 bytes of padding, on 64-bit systems
-        buf.advance(4);
-
-        // FIXME: check that hdr.xlp_rem_len matches self.contlen
-        //println!("next xlog page (xlp_rem_len: {})", hdr.xlp_rem_len);
-
-        hdr
-    }
-
-    #[allow(non_snake_case)]
-    fn decode_XLogLongPageHeaderData(&mut self) -> XLogLongPageHeaderData {
-        let hdr: XLogLongPageHeaderData = XLogLongPageHeaderData {
-            std: self.decode_XLogPageHeaderData(),
-            xlp_sysid: self.inputbuf.get_u64_le(),
-            xlp_seg_size: self.inputbuf.get_u32_le(),
-            xlp_xlog_blcksz: self.inputbuf.get_u32_le(),
-        };
-
-        hdr
-    }
 }
 
 #[allow(dead_code)]
diff --git a/postgres_ffi/src/xlog_utils.rs b/postgres_ffi/src/xlog_utils.rs
index 22f8232f24..5d1ed5b456 100644
--- a/postgres_ffi/src/xlog_utils.rs
+++ b/postgres_ffi/src/xlog_utils.rs
@@ -301,8 +301,23 @@ pub struct XLogPageHeaderData {
     pub xlp_tli: u32,      /* TimeLineID of first record on page */
     pub xlp_pageaddr: u64, /* XLOG address of this page */
     pub xlp_rem_len: u32,  /* total len of remaining data for record */
+    padding: u32,          /* Add explicit padding */
 }
 
+impl XLogPageHeaderData {
+    pub fn from_bytes<B: Buf>(buf: &mut B) -> XLogPageHeaderData {
+        XLogPageHeaderData {
+            xlp_magic: buf.get_u16_le(),
+            xlp_info: buf.get_u16_le(),
+            xlp_tli: buf.get_u32_le(),
+            xlp_pageaddr: buf.get_u64_le(),
+            xlp_rem_len: buf.get_u32_le(),
+            padding: buf.get_u32_le(),
+        }
+    }
+}
+
+
 #[repr(C)]
 #[derive(Debug)]
 pub struct XLogLongPageHeaderData {
@@ -311,3 +326,14 @@ pub struct XLogLongPageHeaderData {
     pub xlp_seg_size: u32,       /* just as a cross-check */
     pub xlp_xlog_blcksz: u32,    /* just as a cross-check */
 }
+
+impl XLogLongPageHeaderData {
+    pub fn from_bytes<B: Buf>(buf: &mut B) -> XLogLongPageHeaderData {
+        XLogLongPageHeaderData {
+            std: XLogPageHeaderData::from_bytes(buf),
+            xlp_sysid: buf.get_u64_le(),
+            xlp_seg_size: buf.get_u32_le(),
+            xlp_xlog_blcksz: buf.get_u32_le(),
+        }
+    }
+}