dotcloud/docker

package container // import "github.com/docker/docker/container"

import (
    "strings"
)

// ReplaceOrAppendEnvValues returns the defaults with the overrides either
// replaced by env key or appended to the list
func ReplaceOrAppendEnvValues(defaults, overrides []string) []string {
    cache := make(map[string]int, len(defaults))
    for i, e := range defaults {
        index := strings.Index(e, "=")
        cache[e[:index]] = i
    }

    for _, value := range overrides {
        // Values w/o = means they want this env to be removed/unset.
        index := strings.Index(value, "=")
        if index < 0 {
            // no "=" in value
            if i, exists := cache[value]; exists {
                defaults[i] = "" // Used to indicate it should be removed
            }
            continue
        }

        if i, exists := cache[value[:index]]; exists {
            defaults[i] = value
        } else {
            defaults = append(defaults, value)
        }
    }

    // Now remove all entries that we want to "unset"
    for i := 0; i < len(defaults); i++ {
        if defaults[i] == "" {
            defaults = append(defaults[:i], defaults[i+1:]...)
            i--
        }
    }

    return defaults
}