hsperfdata

import (
    "fmt"
    "log"

    "github.com/xin053/hsperfdata"
)

// first, you should get the file path string of the hsperfdata file that you want to parser.
// there are several function to get the path, include PerfDataPath(pid string), PerfDataPaths(pids []string), UserPerfDataPaths(user string), CurrentUserPerfDataPaths(), AllPerfDataPaths(), DataPathsByProcessName(processName string)
// the source code is easy to read through, you can just read the hsperfdata.go to figure out how to use them.

entryMap, err := hsperfdata.ReadPerfData(filePath, true)
if err != nil {
    log.Fatal("open fail", err)
}

for _, key := range keys {
    fmt.Printf("%s=%v\n", key, entryMap[key])
}

export GOPATH=`pwd`
go get -d github.com/xin053/hsperfdata
cd src/github.com/xin053/hsperfdata
go build cli.exe

// perfdataHeader http://openjdk.java.net/groups/serviceability/jvmstat/sun/jvmstat/perfdata/monitor/AbstractPerfDataBufferPrologue.html
// source code https://github.com/dmlloyd/openjdk/blob/jdk/jdk/src/jdk.internal.jvmstat/share/classes/sun/jvmstat/perfdata/monitor/AbstractPerfDataBufferPrologue.java
type perfdataHeader struct {
    Magic     uint32 // magic number - 0xcafec0c0
    ByteOrder byte   // big_endian == 0, little_endian == 1
    Major     byte   // major version numbers
    Minor     byte   // minor version numbers
    // ReservedByte byte   // used as Accessible flag at performance data V2
}

// prologue http://openjdk.java.net/groups/serviceability/jvmstat/sun/jvmstat/perfdata/monitor/v2_0/PerfDataBufferPrologue.html
// source code https://github.com/dmlloyd/openjdk/blob/jdk/jdk/src/jdk.internal.jvmstat/share/classes/sun/jvmstat/perfdata/monitor/v2_0/PerfDataBufferPrologue.java
type bufferPrologueV2 struct {
    Accessible   byte  // Accessible flag at performance data V2
    Used         int32 // number of PerfData memory bytes used
    Overflow     int32 // number of bytes of overflow
    ModTimestamp int64 // time stamp of the last structural modification
    EntryOffset  int32 // offset of the first PerfDataEntry
    NumEntries   int32 // number of allocated PerfData entries
}

// entryHeader http://openjdk.java.net/groups/serviceability/jvmstat/sun/jvmstat/perfdata/monitor/v2_0/PerfDataBuffer.html
// source code https://github.com/dmlloyd/openjdk/blob/jdk/jdk/src/jdk.internal.jvmstat/share/classes/sun/jvmstat/perfdata/monitor/v2_0/PerfDataBuffer.java
type entryHeader struct {
    EntryLength  int32 // entry length in bytes
    NameOffset   int32 // offset to entry name, relative to start of entry
    VectorLength int32 // length of the vector. If 0, then scalar.
    DataType     byte  // JNI field descriptor type
    Flags        byte  // miscellaneous attribute flags 0x01 - supported
    DataUnits    byte  // unit of measure attribute
    DataVar      byte  // variability attribute
    DataOffset   int32 // offset to data item, relative to start of entry.
}