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