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Host introspection: Difference between revisions
→{{header|Go}}: Put back completely non-portable /proc hack but and some comments
(→{{header|Go}}: Replace /proc hack) |
(→{{header|Go}}: Put back completely non-portable /proc hack but and some comments) |
||
Line 261:
import (
"fmt"
"io/ioutil"
"runtime"
"strconv"
"strings"
"unsafe"
)
Line 279 ⟶ 281:
fmt.Println("mixed endian?")
}
// Usually one cares about the size the executible was compiled for
// rather than the actual underlying host's size.
// There are several ways of determining the size of an int/uint.
fmt.Println(" strconv.IntSize =", strconv.IntSize)
// That uses the following definition
intSize := 32 << uint(^uint(0)>>63)
fmt.Println("32 << uint(^uint(0)>>63) =", intSize)
Line 293 ⟶ 298:
fmt.Println(" sizeof(int) in bits:", unsafe.Sizeof(int(0))*bitsPerByte)
fmt.Println(" sizeof(uintptr) in bits:", unsafe.Sizeof(uintptr(0))*bitsPerByte)
// If we really want to know the architecture size
// compiled for and not the size of int it safest to take the max of those.
archSize := unsafe.Sizeof(int(0))
if psize := unsafe.Sizeof(uintptr(0)); psize > archSize {
archSize = psize
}
fmt.Println(" compiled
// There are some *very* unportable ways to attempt to get the actual
// underlying hosts' word size.
// Inspect cpuinfo to determine word size (some unix-like OS' only).
c, err := ioutil.ReadFile("/proc/cpuinfo")
if err != nil {
fmt.Println(err)
return
}
ls := strings.Split(string(c), "\n")
for _, l := range ls {
if strings.HasPrefix(l, "flags") {
for _, f := range strings.Fields(l) {
if f == "lm" { // "long mode"
fmt.Println("64 bit word size")
return
}
}
fmt.Println("32 bit word size")
return
}
}
}</lang>
{{out}}
Line 309 ⟶ 336:
sizeof(int) in bits: 64
sizeof(uintptr) in bits: 64
compiled
open /proc/cpuinfo: no such file or directory
</pre>
<pre>
Line 318 ⟶ 346:
sizeof(int) in bits: 32
sizeof(uintptr) in bits: 32
compiled
open /proc/cpuinfo: no such file or directory
</pre>
<pre>
Line 327 ⟶ 356:
sizeof(int) in bits: 32
sizeof(uintptr) in bits: 32
compiled
open /proc/cpuinfo: No such file or directory
</pre>
Alternative technique:
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