feat: Use atomic writes for progress updates (#1319)

src/progress.sh

@@ -2,6 +2,7 @@
 set -Eeuo pipefail
 
 info="/run/shm/msg.html"
+info_tmp="${info}.${BASHPID}.tmp"
 
 escape() {
 
@@ -17,6 +18,23 @@ escape() {
   return 0
 }
 
+writeInfo() {
+
+  local content="$1"
+
+  if ! printf '%s\n' "$content" > "$info_tmp"; then
+    rm -f -- "$info_tmp"
+    return 1
+  fi
+
+  if ! mv -f -- "$info_tmp" "$info"; then
+    rm -f -- "$info_tmp"
+    return 1
+  fi
+
+  return 0
+}
+
 getBytes() {
 
   local path="$1"
@@ -48,6 +66,24 @@ getBytes() {
   return 0
 }
 
+getStatus() {
+
+  local file="$1"
+  local bytes total extra=""
+
+  [ -r "$file" ] || return 1
+  read -r bytes total extra < "$file" || return 1
+
+  if [[ ! "$bytes" =~ ^[0-9]+$ ||
+        ! "$total" =~ ^[0-9]+$ ||
+        -n "$extra" ]]; then
+    return 1
+  fi
+
+  printf '%s %s\n' "$bytes" "$total"
+  return 0
+}
+
 formatSize() {
 
   local bytes="$1"
@@ -117,7 +153,9 @@ printSizeProgress() {
   return 0
 }
 
-finishLogProgress() {
+finishProgress() {
+
+  rm -f -- "$info_tmp"
 
   if [[ "$output" == "log" && "$printed" == "Y" ]]; then
     printf '\n'
@@ -132,6 +170,7 @@ body=$(escape "$3")
 output="${4:-}"
 step_bytes="${5:-536870912}"
 mode="${6:-apparent}"
+status_file="${7:-}"
 
 if [[ -n "$total" && ! "$total" =~ ^(0|[1-9][0-9]*)$ ]]; then
   printf 'Invalid total size: %s\n' "$total" >&2
@@ -168,7 +207,7 @@ if [ -z "$total" ] || [[ "$total" == "0" ]]; then
   log_mode="size"
 fi
 
-trap finishLogProgress EXIT
+trap finishProgress EXIT
 trap 'exit 0' HUP INT QUIT TERM
 
 if [[ "$body" == *"..." ]]; then
@@ -178,12 +217,32 @@ fi
 while true; do
 
   bytes=$(getBytes "$path" "$mode")
+  effective_total="$total"
+
+  if [ -n "$status_file" ] && status=$(getStatus "$status_file"); then
+    read -r status_bytes status_total <<< "$status"
+    bytes="$status_bytes"
+
+    if (( status_total > 0 )); then
+      effective_total="$status_total"
+    fi
+  fi
+
+  # A real total may become available shortly after aria2 starts.
+  if [[ "$log_mode" == "size" &&
+        "$printed" == "N" &&
+        -n "$effective_total" &&
+        "$effective_total" != "0" ]]; then
+    log_mode="percent"
+  fi
 
   if (( bytes > 4096 )); then
 
     write_html="Y"
 
-    if [ -z "$total" ] || [[ "$total" == "0" ]] || (( bytes > total )); then
+    if [ -z "$effective_total" ] ||
+        [[ "$effective_total" == "0" ]] ||
+        (( bytes > effective_total )); then
       size=$(formatSize "$bytes")
 
       if [[ "$output" == "log" ]]; then
@@ -197,7 +256,7 @@ while true; do
       fi
     else
       # Truncate to one decimal so progress is never reported early.
-      progress=$((bytes * 1000 / total))
+      progress=$((bytes * 1000 / effective_total))
       (( progress > 1000 )) && progress=1000
 
       percent=$((progress / 10))
@@ -219,7 +278,7 @@ while true; do
     fi
 
     if [[ "$write_html" == "Y" ]]; then
-      printf '%s\n' "${body//(\[P\])/($size)}" > "$info"
+      writeInfo "${body//(\[P\])/($size)}"
     fi
   fi
 

src/socket.sh

@@ -3,6 +3,8 @@ set -Eeuo pipefail
 
 lastmsg=""
 path="/run/shm/msg.html"
+dir=$(dirname -- "$path")
+name=$(basename -- "$path")
 
 refresh() {
 
@@ -17,15 +19,26 @@ refresh() {
 
   lastmsg="$msg"
   echo "s: $msg"
+
   return 0
 }
 
 refresh
 
-inotifywait -m "$path" |
-  while read -r fp event fn; do
+inotifywait \
+  -m -q \
+  -e close_write,moved_to,delete \
+  --format '%e %f' \
+  "$dir" |
+  while read -r event file; do
+
+    [[ "$file" == "$name" ]] || continue
+
     case "${event,,}" in
-      "modify"* ) refresh ;;
-      "delete_self" ) echo "c: vnc" ;;
-    esac    
+      "delete"* )
+        echo "c: vnc" ;;
+      "close_write"* | "moved_to"* )
+        refresh ;;
+    esac
+
   done

src/utils.sh

@@ -300,6 +300,25 @@ writeFile() {
   return 0
 }
 
+writeAtomic() {
+
+  local path="$1"
+  local content="$2"
+  local tmp="${path}.${BASHPID}.tmp"
+
+  if ! printf '%s\n' "$content" > "$tmp"; then
+    rm -f -- "$tmp"
+    return 1
+  fi
+
+  if ! mv -f -- "$tmp" "$path"; then
+    rm -f -- "$tmp"
+    return 1
+  fi
+
+  return 0
+}
+
 readFile() {
 
   local path="$1"
@@ -411,8 +430,8 @@ html() {
   HTML="${HTML/\[4\]/$footer}"
   HTML="${HTML/\[5\]/$FOOTER2}"
 
-  echo "$HTML" > "$PAGE" || return 1
-  echo "$body" > "$INFO" || return 1
+  writeAtomic "$PAGE" "$HTML" || return 1
+  writeAtomic "$INFO" "$body" || return 1
 
   return 0
 }