Documentation
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Overview ¶
Package aba decodes and validates an ABA routing transit number (RTN) — the 9-digit code that identifies a US bank or credit union in ACH and wire transfers. It is the US-domestic counterpart to internal/iban (the international account): a routing number turns up in ACH-fraud / business-email-compromise lures, leaked direct-deposit forms, and check images, so decoding one off a paste tells an operator whether the number is internally consistent and which Federal Reserve district issued it.
Wrap-vs-native judgement ¶
Native. An RTN is a fixed digit-field layout — a 4-digit Federal Reserve routing symbol, a 4-digit ABA institution identifier, and 1 check digit — guarded by a weighted modulus-10 checksum. Validating it is integer arithmetic plus a small fixed range classification; no runtime dependency or hand-transcribed lookup beyond the 12 statutory Federal Reserve districts is justified. stdlib only, no new go.mod dep.
Verifiable / no confidently-wrong output ¶
The modulus-10 checksum is the verification anchor — it is recomputed and compared, and a mismatch is reported as checksum_valid=false with a note (a mistyped RTN), never asserted as a definitively fake bank. The Federal Reserve district and the institution type are derived from the leading two digits by the published numbering ranges (not a guess); a prefix outside those ranges leaves the district undetermined rather than inventing one. The institution identifier is surfaced raw — it maps to a specific bank only via the proprietary American Bankers Association registry, which is not embedded.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Result ¶
type Result struct {
RoutingNumber string `json:"routing_number"`
RoutingSymbol string `json:"federal_reserve_routing_symbol"` // digits 1-4
InstitutionID string `json:"aba_institution_identifier"` // digits 5-8
CheckDigit string `json:"check_digit"` // digit 9
Type string `json:"type"` // Government / Primary / Thrift / Electronic / Traveler's
District int `json:"federal_reserve_district,omitempty"`
DistrictName string `json:"federal_reserve_district_name,omitempty"`
ChecksumValid bool `json:"checksum_valid"` // ABA weighted modulus-10 (the verification anchor)
Notes []string `json:"notes,omitempty"`
}
Result is the decoded view of an ABA routing transit number.
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