Having a look at http://associates-amazon.s3.amazonaws.com/signed-requests/helper/index.html
The following Name-Value Pairs:
Service=AWSECommerceService
Version=2011-08-01
AssociateTag=PutYourAssociateTagHere
Operation=ItemSearch
SearchIndex=Books
Keywords=harry+potter
Timestamp=2015-09-26T14:10:56.000Z
AWSAccessKeyId=123
The name-value pairs have been sorted according to byte-order
Should result in
AWSAccessKeyId=123
AssociateTag=PutYourAssociateTagHere
Keywords=harry%20potter
Operation=ItemSearch
SearchIndex=Books
Service=AWSECommerceService
Timestamp=2015-09-26T14%3A10%3A56.000Z
Version=2011-08-01
How to achieve this in R?
As far as i can tell they are sorted by their
as.numeric(charToRaw(name))
values. If the first value is equal then they are sorted by the second one, then the third and so on.
Question: How to do this in R?
# Name-Value-Pairs
nvp <- list(
"Service"="AWSECommerceService",
"Version"="2011-08-01",
"AssociateTag"="PutYourAssociateTagHere",
"Operation"="ItemSearch",
"SearchIndex"="Books",
"Keywords"="harry potter",
"Timestamp"="2015-09-26T14:10:56.000Z",
"AWSAccessKeyId"="123"
)
Get Bytes:
bytes <- function(chr){
as.data.frame(t(as.numeric(charToRaw(chr))))
}
Calculate Bytes, and rbind the values
b <- lapply(names(nvp), bytes)
b <- data.table::rbindlist(b, fill=TRUE) # other than base::rbind, this fills by NA
Order the names by first column, then by second, by third, ... and so on
names(nvp)[do.call(order, as.list(b))]
[1] "AWSAccessKeyId" "AssociateTag" "Keywords" "Operation" "SearchIndex"
[6] "Service" "Timestamp" "Version"
So finally nvp[do.call(order, as.list(b))]
returns in the properly sorted list
The answer above from @Floo0 is very good and is even more useful when combined with the encrypted signature from this answer.
I was stuck until I found these two posts. I used Amazon's Signed Request Helper to verify that I successfully signed my query. Use the code above to properly canonically sort the query and this code (again found here) to sign it:
library(digest)
library(RCurl)
curlEscape(
base64(
hmac(enc2utf8((secret_key)),
enc2utf8(string_to_sign),
algo = 'sha256',
serialize = FALSE,
raw = TRUE)
)
)
Also, I have not used it yet, but there is a Python module, amazon-product-api
, that seems to be less work.