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Change the hash function to be more format tolerant #3610

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merged 1 commit into from
May 13, 2019
+14 −57
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Change the hash function to be more format tolerant #3610

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71 changes: 14 additions & 57 deletions google/resource_compute_backend_service.go
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Original file line number Diff line number Diff line change
Expand Up @@ -50,13 +50,16 @@ func resourceGoogleComputeBackendServiceBackendHash(v interface{}) int {
v = ""
}

buf.WriteString(fmt.Sprintf("%s-", v.(string)))
buf.WriteString(fmt.Sprintf("%v-", v))
}
if v, ok := m["capacity_scaler"]; ok {
if v == nil {
v = 0.0
}

// floats can't be added to the hash with %v as the other values are because
// %v and %f are not equivalent strings so this must remain as a float so that
// the hash function doesn't return something else.
buf.WriteString(fmt.Sprintf("%f-", v.(float64)))
}
if v, ok := m["description"]; ok {
Expand All @@ -65,93 +68,47 @@ func resourceGoogleComputeBackendServiceBackendHash(v interface{}) int {
}

log.Printf("[DEBUG] writing description %s", v)
buf.WriteString(fmt.Sprintf("%s-", v.(string)))
buf.WriteString(fmt.Sprintf("%v-", v))
}
if v, ok := m["max_rate"]; ok {
if v == nil {
v = 0
}

buf.WriteString(fmt.Sprintf("%d-", int64(v.(int))))
buf.WriteString(fmt.Sprintf("%v-", v))
}
if v, ok := m["max_rate_per_instance"]; ok {
if v == nil {
v = 0.0
}

// floats can't be added to the hash with %v as the other values are because
// %v and %f are not equivalent strings so this must remain as a float so that
// the hash function doesn't return something else.
buf.WriteString(fmt.Sprintf("%f-", v.(float64)))
}
if v, ok := m["max_connections"]; ok {
if v == nil {
v = 0
}

switch v := v.(type) {
case float64:
// The Golang JSON library can't tell int values apart from floats,
// because MM doesn't give fields strong types. Since another value
// in this block was a real float, it assumed this was a float too.
// It's not.
// Note that math.Round in Go is from float64 -> float64, so it will
// be a noop. int(floatVal) truncates extra parts, so if the float64
// representation of an int falls below the real value we'll have
// the wrong value. eg if 3 was represented as 2.999999, that would
// convert to 2. So we add 0.5, ensuring that we'll truncate to the
// correct value. This wouldn't remain true if we were far enough
// from 0 that we were off by > 0.5, but no float conversion *could*
// work correctly in that case. 53-bit floating types as the only
// numeric type was not a good idea, thanks Javascript.
var vInt int
if v < 0 {
vInt = int(v - 0.5)
} else {
vInt = int(v + 0.5)
}

log.Printf("[DEBUG] writing float value %f as integer value %v", v, vInt)
buf.WriteString(fmt.Sprintf("%d-", vInt))
default:
buf.WriteString(fmt.Sprintf("%d-", int64(v.(int))))
}
buf.WriteString(fmt.Sprintf("%v-", v))
}
if v, ok := m["max_connections_per_instance"]; ok {
if v == nil {
v = 0
}

switch v := v.(type) {
case float64:
// The Golang JSON library can't tell int values apart from floats,
// because MM doesn't give fields strong types. Since another value
// in this block was a real float, it assumed this was a float too.
// It's not.
// Note that math.Round in Go is from float64 -> float64, so it will
// be a noop. int(floatVal) truncates extra parts, so if the float64
// representation of an int falls below the real value we'll have
// the wrong value. eg if 3 was represented as 2.999999, that would
// convert to 2. So we add 0.5, ensuring that we'll truncate to the
// correct value. This wouldn't remain true if we were far enough
// from 0 that we were off by > 0.5, but no float conversion *could*
// work correctly in that case. 53-bit floating types as the only
// numeric type was not a good idea, thanks Javascript.
var vInt int
if v < 0 {
vInt = int(v - 0.5)
} else {
vInt = int(v + 0.5)
}

log.Printf("[DEBUG] writing float value %f as integer value %v", v, vInt)
buf.WriteString(fmt.Sprintf("%d-", vInt))
default:
buf.WriteString(fmt.Sprintf("%d-", int64(v.(int))))
}
buf.WriteString(fmt.Sprintf("%v-", v))
}
if v, ok := m["max_rate_per_instance"]; ok {
if v == nil {
v = 0.0
}

// floats can't be added to the hash with %v as the other values are because
// %v and %f are not equivalent strings so this must remain as a float so that
// the hash function doesn't return something else.
buf.WriteString(fmt.Sprintf("%f-", v.(float64)))
}

Expand Down