1 files changed, 67 insertions, 0 deletions
diff --git a/internal/flamegraph/collapsed.go b/internal/flamegraph/collapsed.go
new file mode 100644
index 0000000..9431d6f
--- /dev/null
+++ b/internal/flamegraph/collapsed.go
@@ -0,0 +1,67 @@
+package flamegraph
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/DataDog/zstd"
+)
+
+type Collapsed struct {
+	iorFile    string
+	fields     []string
+	countField string
+}
+
+func NewCollapsed(iorFile string, fields []string, countField string) Collapsed {
+	return Collapsed{iorFile: iorFile, fields: fields, countField: countField}
+}
+
+// TODO: Write into collapsed.zst (zstd compressed) file
+func (c Collapsed) Write(iorDataFile string) (string, error) {
+	outFile := fmt.Sprintf("%s.%s-by-%s.collapsed.zst",
+		strings.TrimSuffix(iorDataFile, ".ior.zst"),
+		strings.Join(c.fields, ":"),
+		c.countField,
+	)
+
+	if _, err := os.Stat(outFile); err == nil {
+		fmt.Println(outFile, "already exists!")
+		return outFile, nil
+	}
+
+	// outFD should be zstd compressed
+	outFd, err := os.Create(outFile)
+	if err != nil {
+		return outFile, err
+	}
+	defer outFd.Close()
+
+	fmt.Println("Reading", iorDataFile)
+	iod, err := newIorDataFromFile(iorDataFile)
+	if err != nil {
+		return outFile, err
+	}
+
+	fmt.Println("Writing", outFile)
+	writer := zstd.NewWriter(outFd)
+	if err != nil {
+		return outFile, err
+	}
+	defer writer.Close()
+
+	for record := range iod.iter() {
+		var fieldValues []string
+		for _, fieldName := range c.fields {
+			fieldValues = append(fieldValues, record.StringByName(fieldName))
+		}
+		writer.Write([]byte(fmt.Sprintf("%s = %d\n",
+			strings.Join(fieldValues, ";"),
+			record.cnt.ValueByName(c.countField),
+		)))
+	}
+	writer.Flush()
+
+	return outFile, nil
+}