Dump page data with ltx hexdump (#76)

Author: benbjohnson

cmd/ltx/dump.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/superfly/ltx"
+	"github.com/superfly/ltx/internal"
 )
 
 // DumpCommand represents a command to print the contents of a single LTX file.
@@ -82,6 +83,8 @@ Arguments:
 		}
 
 		fmt.Printf("Frame #%d: pgno=%d\n", i, pageHeader.Pgno)
+		fmt.Print(internal.Hexdump(data))
+		fmt.Println()
 	}
 	fmt.Printf("\n")
 

internal/hexdump.go

@@ -0,0 +1,45 @@
+package internal
+
+import (
+	"bytes"
+	"fmt"
+)
+
+func Hexdump(data []byte) string {
+	prevRow := make([]byte, 16)
+
+	var buf bytes.Buffer
+	var dupWritten bool
+	for i := 0; i < len(data); i += 16 {
+		row := make([]byte, 16)
+		copy(row, data[i:])
+
+		// Write out one line of asterisks to show that we just have duplicate rows.
+		if i != 0 && i+16 < len(data) && bytes.Equal(row, prevRow) {
+			if !dupWritten {
+				dupWritten = true
+				fmt.Fprintln(&buf, "***")
+			}
+			continue
+		}
+
+		// Track previous row so we know when we have duplicates.
+		copy(prevRow, row)
+		dupWritten = false
+
+		fmt.Fprintf(&buf, "%08x  %02x %02x %02x %02x %02x %02x %02x %02x  %02x %02x %02x %02x %02x %02x %02x %02x  |%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s|\n", i,
+			row[0], row[1], row[2], row[3], row[4], row[5], row[6], row[7],
+			row[8], row[9], row[10], row[11], row[12], row[13], row[14], row[15],
+			toChar(row[0]), toChar(row[1]), toChar(row[2]), toChar(row[3]), toChar(row[4]), toChar(row[5]), toChar(row[6]), toChar(row[7]),
+			toChar(row[8]), toChar(row[9]), toChar(row[10]), toChar(row[11]), toChar(row[12]), toChar(row[13]), toChar(row[14]), toChar(row[15]),
+		)
+	}
+	return buf.String()
+}
+
+func toChar(b byte) string {
+	if b < 32 || b > 126 {
+		return "."
+	}
+	return string(b)
+}