From 2f621416f69e522f412e34ebbf29e655541414bd Mon Sep 17 00:00:00 2001
From: Owen Jacobson <owen@grimoire.ca>
Date: Sat, 5 Oct 2024 01:15:41 -0400
Subject: Use the right functions for determining error messages.

---
 src/db/backup.rs | 57 +++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 23 deletions(-)

(limited to 'src/db/backup.rs')

diff --git a/src/db/backup.rs b/src/db/backup.rs
index a6fe917..212fa4e 100644
--- a/src/db/backup.rs
+++ b/src/db/backup.rs
@@ -6,7 +6,8 @@ use std::{
 
 use libsqlite3_sys::{
     sqlite3, sqlite3_backup, sqlite3_backup_finish, sqlite3_backup_init, sqlite3_backup_step,
-    sqlite3_errmsg, sqlite3_extended_errcode, SQLITE_BUSY, SQLITE_LOCKED, SQLITE_OK,
+    sqlite3_errmsg, sqlite3_errstr, sqlite3_extended_errcode, SQLITE_BUSY, SQLITE_LOCKED,
+    SQLITE_OK,
 };
 use sqlx::sqlite::SqlitePool;
 
@@ -43,7 +44,7 @@ impl<'p> Backup<'p> {
 
         let handle = Self::start(to.as_raw_handle(), from.as_raw_handle())?;
         let step_result = Self::step(handle, -1);
-        Self::finish(to.as_raw_handle(), handle)?;
+        Self::finish(handle)?;
 
         step_result
     }
@@ -63,10 +64,7 @@ impl<'p> Backup<'p> {
             sqlite3_backup_init(to.as_ptr(), name.as_ptr(), from.as_ptr(), name.as_ptr())
         };
         if handle.is_null() {
-            Err(Error::Backup {
-                code: Error::code_for(to),
-                message: Error::message_for(to),
-            })?;
+            Err(Error::from_handle(to))?;
         }
         // Having proven that `handle` is not null, we could use new_unchecked here.
         // Choosing not to so that any mistakes are caught, rather than causing
@@ -76,30 +74,19 @@ impl<'p> Backup<'p> {
 
     fn step(handle: NonNull<sqlite3_backup>, pages: c_int) -> Result<(), Error> {
         let step = unsafe { sqlite3_backup_step(handle.as_ptr(), pages) };
-        if SQLITE_BUSY == step {
-            Err(Error::Backup {
-                code: step,
-                message: String::from("database busy"),
-            })
-        } else if SQLITE_LOCKED == step {
-            Err(Error::Backup {
-                code: step,
-                message: String::from("database locked"),
-            })
+        if [SQLITE_BUSY, SQLITE_LOCKED].contains(&step) {
+            Err(Error::from_code(step))
         } else {
             Ok(())
         }
     }
 
-    fn finish(to: NonNull<sqlite3>, handle: NonNull<sqlite3_backup>) -> Result<(), Error> {
+    fn finish(handle: NonNull<sqlite3_backup>) -> Result<(), Error> {
         let finished = unsafe { sqlite3_backup_finish(handle.as_ptr()) };
-        if finished == SQLITE_OK {
+        if SQLITE_OK == finished {
             Ok(())
         } else {
-            Err(Error::Backup {
-                code: finished,
-                message: Error::message_for(to),
-            })
+            Err(Error::from_code(finished))
         }
     }
 }
@@ -113,14 +100,38 @@ pub enum Error {
 }
 
 impl Error {
+    pub fn from_handle(handle: NonNull<sqlite3>) -> Self {
+        Self::Backup {
+            code: Self::code_for(handle),
+            message: Self::message_for(handle),
+        }
+    }
+
+    pub fn from_code(code: c_int) -> Self {
+        Self::Backup {
+            code,
+            message: Self::message_from_code(code),
+        }
+    }
+
     fn code_for(handle: NonNull<sqlite3>) -> c_int {
         unsafe { sqlite3_extended_errcode(handle.as_ptr()) }
     }
 
     fn message_for(handle: NonNull<sqlite3>) -> String {
-        let msg = unsafe { sqlite3_errmsg(handle.as_ptr()) };
+        Self::message_from(|| unsafe { sqlite3_errmsg(handle.as_ptr()) })
+    }
+
+    fn message_from_code(code: c_int) -> String {
+        Self::message_from(|| unsafe { sqlite3_errstr(code) })
+    }
+
+    fn message_from(f: impl FnOnce() -> *const i8) -> String {
+        let msg = f();
         debug_assert!(!msg.is_null());
         from_utf8(unsafe { CStr::from_ptr(msg) }.to_bytes())
+            // This is actually promised in the Sqlite3 docs, but we check anyways to catch
+            // mistakes. See <https://www.sqlite.org/c3ref/errcode.html>.
             .expect("error messages from sqlite are always utf-8")
             .to_owned()
     }
-- 
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